I have plenty of gripes with it, enough to write three beefy pages, but the one you refer to is not exclusively about a ladder but about the complete absence of any goal in the game. The best and easiest way for them to remedy this would be to start doing ladder seasons like in D2, but it's not the only example of a gameplay goal. I mentioned other examples, I'm sure you didn't intentionally skip them. What it boils down to is the fact that D3's gameplay doesn't lead to any final purpose, there's nothing to work towards other than just continued grinding for the sake of grinding itself. D2 had ladder competition, season resets, PvP and meaningful wealth as possible long-term goals.So basically your one gripe with D3 is the lack of a ladder?
D3 lacks all of these either because they're completely absent (ladder competition, season resets) or because they're rendered pointless by awful design (PvP, wealth acquisition). As a result, the only ones who were able to enjoy the game for more than a brief spell were the ones who are satisfied with the simple act of killing monsters without any concern for the broader aspects of gameplay (or lack thereof). D3 has the long-term playing facilities of Minesweeper without the high score. Anybody who is at all concerned with their accomplishments being meaningful, challenging, visible, or measurable against others in some way will find nothing in D3, and that is a large part of the reason it will be remembered as perhaps the most notable failure in video game history, taking into account who made it and how good it could realistically have been expected to be.