More of this is skill than class, it really is, but people don't like to admit it, no one wants to think the problem is themselves and blame it on something easy (I'm talking about DPS here) it's fine it's a new game, learning takes time.
A well played Esper, Medic or SS will not be a hindrance, or unwanted or anywhere close to bottom dps.
Espers need mobility improvements in some areas, Medics need a slight single target buff, AoE is great, Spellslingers honestly feel perfectly fine to me, it's nowhere near Warrior level of monkey smash, but it's not bad at all.
All need a few bug fixes and QoL improvements that will help in that regard as well.
Warriors are being brought down, and I imagine Engineer will end up with a few tweaks sooner than later.
The main problem with Warriors are they are incredibly easy to play, they aren't easy to play, hard to master, they are just easy.
Personally I enjoy hard to master classes myself.