Why do long time players play the game so differently?

[dspguy]

The veteran players played like the OP played back in 2013 and 2014. They did all the new stuff. They strived to play the best they possibly could, etc etc. Then they moved on. They realized that all that min-maxing doesn't usually add up to much. All that grinding for gear in content that you don't need the gear to clear it and just becomes moot a few months later when everybody can get an upgrade to better crafted gear on Day 1 of next tier... They don't play the MB because many have enough gil to last the lifetime of the game.

OP, you'll see for yourself after you become the veteran. You'll find yourself grinding old content for achievements, mounts, or whatever it is you find fun.

Mind you, there are still plenty of veterans out there doing all the things you claim they aren't doing such as trying to get better and relearn the job when the abilities change. However, there are also plenty out there where I think that statement does apply.