I guess I haven't gotten to the point in ESO where you're forced to buy stuff hehe :3 But I mean most games are gonna require money at some point, if you want to get everything out of them. For Guild Wars 2 (and I think ESO) you can play the majority of the game for free, but if you care a lot about doing endgame stuff or getting the best items, then you have to pay at that point. Otherwise, how would they make money? Ads don't pay the bills, even for crappy phone games, much less a huge MMO.
So, if you're looking for a "good" MMO you can play entirely for free, those don't exist, to my knowledge. The fully free ones are bad cause they don't have a budget, hehe. Maybe there are some you might enjoy, depending on what you're into (Neverwinter and Star Trek Online and The Secret World seem to be popular, but I personally find them too buggy and awkward to play)
As for the closest to a good free to play MMO, ESO is it... Guild Wars 2 is close, depending on what you want out of it. I think even with the paid content, it doesn't have enough to it.
My personal favorites are WoW and FF14, both have a ton of things to do, a huge population (the Legion expansion for WoW is great and really popular), but they both have subscriptions to support all the content.