I wish I was as good as you! I was past 50 when I took up chess. I know I'll never be be more than a "poor" player, as I took it up so late. Take a look at The Rookie by Stephen Moss. It's a good read and the premise of the book is his struggle to improve his "stalled" grading.
I've been playing for decades... Can't seem to improve
"... Sure, fast games are fine for practicing openings (not the most important part of the game for most players) and possibly developing decent board vision and tactical 'shots', but the kind of thinking it takes to plan, evaluate, play long endgames, and find deep combinations is just not possible in quick chess. … for serious improvement ... consistently play many slow games to practice good thinking habits. ... I know that a large percentage of my readers almost exclusively play on the internet - after all, you are reading this on the internet, right!? But there is a strong case for at least augmenting internet play with some OTB play, whether in a club or, better yet, a tournament. ... I would guess that players who have never played OTB usually gain 50-100 points of playing strength just from competing in their first long weekend tournament, assuming they play five or more rounds of very slow chess. ... Don't have two day? Try a one-day quad (a round-robin among four similarly rated players). … about 100 slow games a year is a reasonable foundation for ongoing improvement. ... Can't make 100? Then try for 60. If you only play three or fewer tournaments a year and do not play slow chess regularly at a club (or on-line, where G/90 and slower play is relatively rare), then do not be surprised that you are not really improving. ..." - NM Dan Heisman (2002)
https://web.archive.org/web/20140627052239/http://www.chesscafe.com/text/heisman16.pdf

My friend, i'll try to help point by point. It is my opinion, but i'm 40 and i understand well your mood.
1) Every 200 in rating means you should have a win ratio of 3 to 1, meaning if you are playing a weaker -200 points rating opponent, you should win 3 and lose 1. Over the board (i think i can say) everyone plays better, most of it because you are more focused and the sight you have over the board is well better than online. Nakamura apart...
2) answer it on 1), the sight is better, focus is greater
3) chess is a mental game, sometimes we spot everything on sight, somedays it is better just watch tv. If you start losing it is your mind saying to you: chess really?! Best to do anything else, even tatics, watch tutorials or just read a book.
Play slower time controls, probably your mind don't have bullet or blitz agility. Playing many games teach you nothing. You have to play much less games, slower, and analyse them in the end. If you don't do this you are just passing good time.
Just a side note. I could do every courses, train as hell, meet the right people and learn from them, but i never could be a leonardo da vinci. Not everyone are genius, most (almost all) of us are "normal", some good, a small number very good. You can improve of course, but you will find a personal ceilling that with age passing, only tend to be lower and lower. Despite all work and train you may do. This is a rule for all chess players, see kasparov strenght 20 years ago and now. Of course, he is great yet, but very very far from his peak. With 30 you already are in your descendent curve. Don't get mad for it. Have fun with the game, that should be your prime goal.

How do I blow by this 1400 plateau??
Your original post tells it all, should be obvious. Quit 3/2, play 5+ minutes and forget about it. Add more time until you quit hanging pieces every other game. I only rate in the 1400s in 2/1, but give me 5 minutes, and I rate 1800s. So, welcome to the slow mouse input club, sonny.

Maybe, but I'm pretty confident I could teach Forrest Gump to play 1800 level chess.
"Chess is like a box of chocolates. You never know what you might get."

@k2xl -
From your profile you play almost exclusively rapid, blitz and bullet games. Try to play mostly longer time controls, including "daily" chess, so you have time to think about what you should be doing. It makes sense that taking time to think about what you should be doing would promote improvement in your chess skills.
This is not to suggest that you should necessarily play exclusively slow time controls or daily games, but they should be the greater percentage of your games, much more so than speed games which do almost nothing to promote an understanding of how to play the game well. Speed chess tends to be primarily an exercise in moving pieces around faster than your opponent while avoiding checkmate, in hopes that his/her clock runs out sooner than yours.
Here's what IM Jeremy Silman has to say on the topic...
https://www.chess.com/article/view/longer-time-controls-are-more-instructive
And the experience of a FIDE Master...
https://www.chess.com/forum/view/general/how-blitz-and-bullet-rotted-my-brain-don-t-let-it-rot-yours
Also, playing without a good foundation in fundamental chess principles and understanding how to apply them will do little to help you become a good chess player. In order to understand these principles it takes study - there is no easy, quick solution to playing good chess....you have to put in the effort to learn...
Good Chess Books for Beginners and Beyond....
https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond
Good Positional Chess, Planning & Strategy Books for Beginners and Beyond...
https://www.chess.com/blog/RussBell/introduction-to-positional-chess-planning-strategy

I've noticed that many strong players I know were encouraged by parents who played or who had a chess coach. Being taught at a young age is important. The best investment an older player can make is to build a time machine and go back to and facilitate their younger self to have tuition. But really the real challenge in chess is to improve from where you are. I've been playing since 13 or 14 - self taught - and I achieved my highest ECF grade when I was nearly 50. It's the fight itself that counts IMO.

In addition to playing way too many fast games--you have another serious problem--You do not know what your mistakes are?--so you keep making the same mistakes over and over again for thousands of games.
Learn from a stronger player what mistakes you keep repeating.
This has all been great advice. I'm overwhelmed by the responses by everyone thank you. I will try playing more long games (10+). Funny that my brain has trouble slowing down in the long games since I play blitz so often. But over time hopefully I will.
I've found lichess has a very strong game analysis feature where you can learn from your mistakes.

Sounds like a plan is in order. Perhaps ghost of pushwood could recommend a plan?
Something fresh for New Years Day. Along with losing or gaining a few pounds. 3 months and counting folks!

While there are many good suggestions to improve, we all have our limits. Perhaps you are close to being as good as you can get?
In the books I have read by GM Yasser Seirawan, he recounts how he lost many times while learning the game. He started playing around the age of 10 and by the time he was 19 he became World Junior Chess Champion (1979). A year later he was awarded his Grand Master status. Now, I don't much about many other GMs; however, I suspect their stories are similar, it didn't take them decades to reach GM status.
So, if you have been at this for decades, enjoy the game for what it is. However, it is most likely that, other than really taking much more time to practice, study and play slower games, you aren't likely to improve much more. And that's ok. Good luck.

blitz is the crack of chess. smoke all life long you still only good at being connected to ur crack world. in sincerity been there n blitz almost made me give up the game n has cost me real money for damaging w e is close if I got stung etc. composed even if crushed il act as if n be polite. also blitz isn't same chess. it's a psychological mind fuc about feelings to me while chess is blood guts war. it's best way I can relate . I got a 40 year history of wanting to play study learn. blitz chess was like crack addiction for my chess soul.iv never smoked crack but a good lifetimes worth seems so perfectly absurd. blitz is good for ur chess game like crack is for your life. if u smoking rock ur gonna find ur wins in rocks still left after the next one.
What's wrong with me? I'm 31, been playing chess since I was a kid. Have studied from YouTube videos, random training.
If you check my chess.com profile you can see I've played thousands of blitz games over many years on the website. My tactics have risen over time (I enjoy that chart) but my games just suck. I range between 1400-1500 basically for the past few years. I feel like I actually used to be better at chess.
I play blitz (3/2) most of the time. Some observations over the decades:
1. I tend to play better in person - I've played some 2000 rated players (chess.com rated) over the years in person and seem to have a 40% win rate when I play them in person (slower games I usually have an advantage). When I tell them my chess.com rating they are always surprised that it is so low.
2. I often just hang pieces. Maybe it's the premove feature, but I still just throw away pieces online. Sometimes I think when playing in person the fact that I have to touch a piece makes me think slower about the ramifications. It's difficult to simulate that online.
3. I often get in streaks. Sometimes I win 7-8 games in a row and climb 100 pts in a day. Sometimes I lose 7-8 games and it feels like every 1300 player I play is just amazing.
Like I said, I have tried to study openings, traps, etc from online videos and trainings from another site's study feature. I play a lot of tactics (as you can see in my profile) and have decent progression (about 50 points per year), but I keep losing.
Is there such thing as a peak? Does practicing really improve? My strategy has always been to do a mix of tactics every day combined with games with the occasional video/watch stream of supergm online... How do I blow by this 1400 plateau??