kvasir wrote: If you want to improve at anything then you need to pick up on what you are doing wrong and fix that. There isn't much more to it.
I agree that getting rid of your mistakes is part of the improvement cycle, but not the only aspect.
Eradicating blunders doesn't even need much review, it "merely" requires to concentrate while playing, use the time you have and that of your opponent to focus on the board, consider a couple of alternatives each time and be aware of liberties, especially towards the end of the game. All of this adds up to "
playing at the level of your understanding". You will know you have achieved this if the review (with AI) doesn't show any mistakes which you can easily spot yourself, only interesting, "new", insights to learn from. This doesn't necessarily mean there are no big fluctuations in the AI's game evaluation: big fights can be very difficult and choosing the wrong option makes for big swings.
If you are able to play at the level of your understanding, improving your understanding of the game is going to pay dividends. If you're not, then it will rather add to the current frustration.
Better understanding comes from aforementioned review but also from activities like replaying pro games (predictive, with instant feedback) or studying corner patterns (often recurring in games, so with presumable short term effect), or reading upon and practicing endgame techniques, ... or any aspect of the game. As said, such study won't translate to results immediately and requires the ability to convert understanding into playing strength.
A special note can be given to tsumego because it will achieve two things: acquire intuition about local positions and vital points, and build a higher capacity for reading, which will help in the first job of playing to your level of understanding.
Much of the frustration with amateurs' lack of progress comes from a weak link between their study and their game results. People sensitive to such immediate feedback, better choose a
deliberate practice with a strong immediate link to game results. And I think that's what the video kvasir linked to talks about.