I played ESO when it first came out, I quit after around two months so much of any opinion I have is out of date
But while I really liked certain aspects of it, I hated others. At the time there was almost no end game progression outside of just more level grinds, the PVP was fun but not very competitive, and it completely lacked any small pvp or even duels. I thought it was fun, but failed on too many MMO benchmarks to be a good MMO. It didn't have the progression of a game like WoW and didn't have almost anything to make it a sandbox, meaning it was an on-rails MMO with no real end game.
I'm aware they added things like Trials and are planning to add more, I've been keeping a watch on it and I'm rooting for the game, it had good mechanics set up, I'm just waiting for it to flesh out. Though I heard troubling things that they're ignoring the PVP? That'd be upsetting because PVP is the only real reason I'd play that game, I like Elder Scrolls but not enough to just play a game because it's in Tamriel.
Basically I went into it expecting an MMO, and got some weird quasi-mmo with little depth to it's systems. Manual blocking/dodging, class progression, and the actual combat were all excellent. But when I pay a game monthly I expect to play it a lot with lots of progression in it.