As far as I can remember, the talent trees in WoW weren't nearly as flexible as the skill trees in D2 could be. If you played say, Druid in D2, you could either put all your points into Transforming/Summoning or Elemental/Summoning, or you could try to be a pure summoner/transform/elemental and you could do just fine whatever the case.
The biggest flaw of D2's skill system was that people would hoard the skill points until later levels because you would "ruin" your character by dumping them into low-level skills early on, aside from a couple exceptions. They fixed that by adding synergy and skill resets.
In WoW though...I mean, there used to be some crossover between the talent trees, then they simplified it more and more until it's "pick this talent tree and stick to it", which it seems like what D3 is. As I understand though, you can customize individual skills by using runes.
My problem with all that is that choosing what to do with each individual skill is probably way less customization than playing with and finding out a skill spread that you find fun to play.
The stat system of D2 was pretty borked though. Ultimate it came down to "put just enough into STR and DEX for gear, maybe enough DEX to block, then rest into VIT". Kinda wish they'd try to rebalanced that system rather than remove it completely.