I was kind of in the same boat you were: I played probably 150 hours of Morrowind, 300 hours of Oblivion, and probably 250 hours total in Skryim. I was excited to get into the Elder Scrolls Online beta, but the beta was absolutely terrible and honestly removed any hype I previously had for the game.
Fast forward to now and the game has come a long way, all for the better. The voice acting is excellent and plentiful (very few things in the game are lacking voice acting, and it's all just stuff that wouldn't have it anyway like your character's musings about a dead guy). The old game was slow and boring. Now the world seems alive and it's great.
The biggest draw: quests are absolutely everywhere. It has a very "Elder Scrolls" feel in that you can be doing one quest, and get sidetracked by 4-5 other quests that present themselves and before you know it, it's 3AM and you still haven't finished that first quest you set out on.
MMO games have never really "clicked" for me, but this game feels more like a single-player Elder Scrolls game than an MMO because the other people are so easily ignored and are completely unnecessary.
If nothing else, it's worth picking up on sale if you're a fan of The Elder Scrolls. Don't let the fact that it's an MMO put you off.
