what’s the difference between a 800 rated player and a 1200 rated player

From my memory of 1200, that sounds right. I think 1200s are significantly stronger than 800s in tactics. I don't think 1200s generally know much about openings. At that level learning opening lines probably won't get you much.
A WCM at my school believes that tactics are extremely important for beginner improvement, and I think that makes sense (not to say other things aren't important too; of course, develop your pieces, control the center, castle, keep an eye on king safety, put your pieces on active squares etc. if you aren't doing that already, though I will also note that I think 800s already have some grasp of these principles.)

Saw you were about 1200 when you started playing on this account. How did you reach that level in the first place?

I played when I was a kid and went to the megafinals when I was 11… but other than that maybe just had a fairly decent natural ability?? Sounds cocky I guess… I did slip to 1100 briefly I think. But been relatively steady progress (minus the odd dip) since.

Nice. Okay, so you had some playing experience as a kid. For people who start from scratch, 1200 is nontrivial effort.
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I did a little chess in elementary school in like fourth grade or something (my Chinese school had a chess program) so when I started on chess.com I was ~800....so not quite the 1200 you got up to haha. Perhaps I would have been higher with some more experience...but I don't care now, as i just wanna make progress from where i'm at lol.
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For OP in particular, I'd recommend working on positional knowledge....I'm saying this mainly based on one game I just randomly opened....here. I won't make a super thorough analysis but here are some things that jumped out at me.

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From the little I've seen in this and another game, I think OP has some nice tactical grasp for this level (but ofc, always good to improve.) I'm more concerned with other things, and have the suspicion there are some principles OP may not be aware of. OP spends a bunch of moves in the opening pushing pawns to attack a bishop that isn't going to be trapped; in the opening you need to be developing your pieces. Furthermore, it's important to wean yourself off the habit of just attacking for the sake of it. If the opponent can just defend, you have not used your moves well; you could use your moves to better your position (in this case your pawn moves actually make life harder for you.)
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Pushing pawns recklessly in the opening will make it hard for you to castle kingside....one of the major things that happened in the game was king safety fell apart. Also, Bb4+, similarly to the pawn pushes targeting the bishop, looks like a one-move check that doesn't help you; again, you should be using your moves wisely and not playing attacks and checks that don't serve a greater purpose. You then proceed to give up your bishop pair, simultaneously trading off a developed piece while behind in development.
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I'm not sure the idea behind 17...f4, which weakens the king when you already can't castle. I have a friend who hadn't heard that you generally aren't supposed to push pawns in front of your king...wonder if you might be in that boat too.
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All in all, gave me the impression of someone who has probably learned chess from playing oneself and has a decent intuition for the kinds of calculations that may stumble beginners, but needs to learn some other principles which will be vital to reaching 1200 and beyond.

That analysis is way more scientific than mine, thanks.

Oh, didn't even notice that rook....guess I was going through the game quickly, but yeah there was a point black could have turned the tables.

The difference between an 800 and a 1200 is that an 800 rated player simply doesn’t understand the game yet. Like they may (or may not depending on the 800) know how all the pieces move but they literally play the game in a different way. Pawns are there to be pushed, pieces are there to stay right where they are if they aren’t being used in a checkmate threat right this second, the queen is essentially the only piece you need, et cetera et cetera. Meanwhile, a 1200 at least knows about the basics of most stages of chess. They may not have understand them but at least they know they exist, and that alone is usually enough to help. The tactical difference is also massive, on an occasion a game may be won without any gambits or egregious blunders.

@MyRatingIs1523IsBack talks like that, but don't read too much into it. You can use exaggerated language to describe mistakes of any player if you want to.
At your level, I think it's not unseen to not understand the principle of not making "time wasting moves" in @AccuratelyRatedUSCFPlayer's words, but it's certainly not too late to learn. But yes, learn what kind of moves you don't wanna make cuz they weaken your position.