A question about openings

Coincidentally I was watching another Naroditsky video last night when he was more or less saying the same thing.

I agree with him 100%. You don't need to go to extremes and try to memorize a million lines that go all the way into the middlegame. Just the basic ideas of a few openings that you like, learn to spot mistakes by your opponent and how to punish them. You'll win more games and have more fun playing chess.

That is exactly what you do by learning the london system or any other opening but you learn concrete moves by you learn many lines that are safe and what not to do and why etc...learn opening not just principles that are  just general guidelines for beginners... 

https://www.youtube.com/watch?v=8IlJ3v8I4Z8

I would say even studying the wrong way is better than not studying at all.  Daniel has a "Streamer Lessons" playlist on his YT channel where he recorded sessions with students.  I recall seeing a MoistCr1tikal video (not my thing to watch, but was informative) where he taught him a few opening lines and then watched while he played games and played within his newfound knowledge.  Later, they looked at games he played on his own time and analyzed them. This was when he was around 800 or so if I recall correctly.  It was profound how much he improved his game in a very short time just by not losing on move 4.  You have to start somewhere. 

Personally, due to the popular opinion of not studying opening, I avoided it for some time when I began playing again. Only when I could see it was clearly my biggest weakness did I start working on them.  I am now to where I feel confident in most of the common openings, and no longer either lose the game in the opening 10 moves, or essentially lose the game on time by having to burn time 'playing' the opening.  That doesn't count for Daily, but in any time control otherwise, you just can't spend all day on move 3.  

Both approaches have value to them!

Around the listed 900-1000 level it is usually recommended to just avoid deep opening study entirely and just play in alignment with the fundamentals "chess opening principles."

https://www.chess.com/blog/KeSetoKaiba/opening-principles-again 

These general principles work even through Grandmaster level, but are especially useful at the lowest levels since typically the opponent won't follow these concepts accurately and by you doing so you can often gain an advantage.

Once you do pay a bit more attention to specific openings though, both approaches have value to them like I said. If you want to learn a repertoire that you can expand on over time and will serve you well at all levels, then that is great You'll become really knowledgeable with your particular opening (or variations) and gain specialized insight. Choosing "mainline" openings are especially useful for this because they are solid and have stood the test of time against Grandmaster and engine analysis alike.

However, there is also value in mixing up your openings and learning a lot of things well. Doing so will expose you to a broader spectrum of ideas and sometimes concepts in one opening help you navigate other openings due to patterns and similarities. However, it is unlikely to get as specialized ability into a specific opening. 

For my own chess, I tend to focus on a basic repertoire that I can always rely on, but occasionally I'll experiment into other openings for unrated games - this way I can get the best of both worlds

There really isn't a right or wrong between both of these approaches though. Just choose whichever you feel most comfortable with and know that you are always free to "change your mind" and adapt your approach as you see fit.

As long as your opening is sound, you should have a good foundation to improve. Also, try to play some dynamic openings too. I don't know if you do or not but a one system fits all will hinder your progress and you want to have the mindset of punishing your opponent's bad moves.