Teleporting is immersion-breaking, but it's convenient. Who wants to use a taxi system to get everywhere? You can do that when you feel like role playing and immersing yourself, but when you just want to teleport somewhere to unlock a raid that your party is waiting on you really don't want to have to use something like a chocobo porter to get everywhere.

Switching classes to an entirely different gearset without going home is immersion-breaking but again it's giving the player the freedom to role play if they want. If for your personal immersion you don't want to be able to switch classes without going home, you can always travel back to a house before switching. The game just gives you the freedom to not role play if you don't feel like it right now.

I don't agree that there is a lag when characters run around on the screen. If you race someone you may see yourself in front while they see themselves in front but that's true in a lot of games because of ping. Try turning up your system and character settings.

Even with 200 ping, if I move out of red right before the cast ends then I'm out of it. I've been dodging red at 95% of the cast regularly farming the latest raid, and it works every single time.

I don't know what abilities you think are not fun, but on a tank I find my abilities make a difference. I have used my party mitigation or Reprisal many times and resulted in everyone surviving with 1% health, especially when they have vuln stacks, and whenever that happens I know I made a difference and that they would have died otherwise. On a dark knight I sometimes apply my shield to someone low on health who is about to die to a raid-wide AoE and it saves them and sometimes that is the last healer or a red mage, so it makes a difference. In Shadowbringers dungeons you can interrupt the worst casts in trash pulls and if you do it's a lot easier for the healer so it makes a difference as well. I could go on because there are so many more examples of why I find tanking fun.