Through my years of mmo and rpg gaming I've tended to swing between the two extremes of the warrior/wizard dynamic.
Some days I just want to be a dumb tank in full armor soaking up hits and acting as a wall for squishier classes. But then there's days where I love being a glass cannon that can kill something in 1-2 nukes but a strong breeze can kill me.
The least fun I've head with a class was as a healer druid in Everquest. Something so stressful about the party relying on you for heals and if you wipe it's generally your fault. idk how people dedicate themselves to a class like that.
The proletariat
I generally lean towards classes with more mechanical complexity, so generally casters/status effect types. The gameplay loop needs to sate my ADHD, so if all I'm doing is smacking something with a sword by left clicking I'm quickly going to get bored and drop it.