Is it really self-improvement when:
1) There is always new content to clear, which you may not enjoy for having a different difficulty curve, or being more of the same, or having aesthetics/mechanics you don't really like? Off the top of my head, the unskippable cutscenes in certain trials would be very off-putting to older players.
2) Your own main jobs are constantly being reworked: your role diminished/diluted, your ability choice removed, and your rotations gutted? Perhaps you don't want to keep re-learning a job when it will just change again, and often in a less fun way.
3) You have a real life and can discover other interests that translate more directly to benefitting you IRL? Video game burnout is a process that eventually happens to everyone because it is a fairly parasitic pasttime, and that is even allowing for intentionally channeling it in pro-social ways.
All three points just reflect how long the game has been around, and how eventually the divide between various "eras" creates more casual/nostalgic interest in franchise vets. Happens across all media.
And, btw, if it helps categorize my opinion, I am decidedly in the camp of not caring about parsing. I don't have the time or interest in joining a static, and I actually enjoy casual matchups in DF/PF. Not to mention the whole thing feels like a waste of time to me if I'm not ultimately monetizing all those hours sunk into the game, be it through streaming or competitive play. I'm not great--I have really on point days and some faffs, oftentimes related to party communication--but the way I play, I don't need to be.