I've played TERA Online in the past, and it's been the only MMORPG I've ever felt attached to, I really liked the world, the gameplay, the aesthetics and classes. Unfortunately it was very grindy and eventually died. There are private servers still running today, and I did try them, but found I don't have the patience to play this style of game anymore.
The closest thing to an MMO I still play is Warframe. Put about 2000 hours into it since starting it back in 2014 (and taking a many years break until recently). Another MMORPG I did enjoy, mostly for the Ragnarok visual style and nostalgia, was Tree of Savior. Sadly that one never took off, kinda wish there was an offline version of it, because it was nice.