IMO people who seem to not improve have the unfortunate predisposition to focus on the wrong things. It's just bad luck that they don't conceptualize chess in terms of e.g. threats and trying to keep material. The way they approach chess might make them fast improvers at different games, but not at chess.
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So anyway, I'd say learn the opening principles
https://www.chess.com/article/view/the-principles-of-the-opening
Read a chess book like this one:
https://www.amazon.com/Back-Basics-Tactics-ChessCafe-Chess/dp/1888690348
And play games.
After that if you're still stuck at the same rating, then sure, maybe you should give up hope of improving.
Is there a specific sign or time or elo which after a good number of games you should resign yourself to never getting better?
I don’t believe I’ll ever improve even after lessons, puzzles, videos, playing many games etc. And I’m just wondering if now is a good time to just give up or something.