The stronger the player, the better they tend to be in the later stages of the game... not only endgames, but also the later middlegame stages... like Q+R+B vs Q+R+N for example. The lower the rating, the faster they trade down, so the less experience they have playing in these in-between stages so to speak.
Anyway, there's nothing magical about the 2200 FIDE line that you "need" some special "mindset." If you began young enough, and work hard enough, you can cross it without even noticing such a line exists...
... although one last note... the difference between someone who only plays online, and someone who has an OTB title is pretty big if the online player switches to OTB. Not only will your opponents tend to be more well rounded, more prepared, and more focused, but some players have trouble adapting to the psychology of OTB play, where you might see your opponent sigh or smirk or etc. Where the tension of a single game is drawn out over hours instead of just minutes, and where you're required to play on a set schedule instead of waiting until the mood and energy level is right.
I've recently heard of this term of a club player (yes I'm uncultured), and they're usually defined as somebody who's about 1300-2100 rated (online), or if we're going to equate that to USCF or FIDE, probably 1500-2000.
What exactly seperates a club player from a chess master (not necessarily titled, like an AGM or even just a 2000 FIDE rated player)? Is it their playstyle being different (club players tend to stick with ideas while chess masters play positionally and neutralize the game)? Or is it simply how we distinguish between a certain rating and a certain rating?
If there is to be differences between a chess master and a club player, how does a club player become a chess master? What do they need to change about their playstyle? Their mindset? Their psychology? Different opening choices? Dedication? I do aim for a title some time in the future (it's ambitious and unlikely, but life is boring nowadays), so I would love to know what's stopping me from playing better chess.
Thanks a lot, and have a nice day.