In a vacuum, Diablo 3 is a good- no, probably a really good game. And understand, by "endgame" people don't mean "shit to do at the end of the game" but rather "a reason to keep playing the game after clearing at the highest difficulty level".
Why is that important? Because this is the sequel to Diablo 2: LoD. Which is probably my favorite game ever, and a game that I *did* play for about ~4 years or so. So, it's got a pretty important lineage to live up to, which I think the consensus is that as of now it's failing to do.
For me, it's maddening because for more than 3/4 of the game, the most important thing (combat) is done just. right. It's kind of like an anti-mmorpg in that sense (suck it e-toilet). It's only in Act 2 inferno and beyond that a combination of shitty drops, dumb champion pack affixes (to the point where community managers actually tell people to restart their game if they get something absurd like fast/reflects damage/jailer/desecrator) etc etc means you don't feel incentivized to play the game the way you enjoyed playing it before... if at all.
I still think that when everything is said and done, the game will be a worthy successor to D2:LoD. Right now though is a pretty boring time if you've made it pretty far along in the game though.