Can you elaborate on why you feel this way?
In general I felt that Diablo 3 had a wide gamut of skills but ultimately there was not an enormous difference between them. In Diablo 2, for comparison, a skellymancer and a melee poison necro are practically two entirely different classes. Same thing for a martial arts assassin or a trapsin or many of the other numerous viable builds.
D3 seemed to have a massive amount of skills available, especially when factoring in runes, but ultimately they all somehow felt and seemed like utilities rather than completely character [re]defining. And the 'locking in' of skills seems likely to even further minimize the relevance of choice. For instance, in D2 every sorceress there is has static field hotkeyed. There will certainly be other similar must-have skills in D3. If a number of your skills are locked in to these must-haves then again your choices for customization go further down.
And the lack of skill specialization makes all the D3 options seem even more diluted. In particular how is equipment supposed to specialize your character when it's impossible to specialize in skills? This isn't a rhetorical question, I'm hoping I just missed an announcement somewhere or something. What I mean here is that in D2 if you find a wand that is +3 to summon skeleton, +3 to skeleton master, +1 to necromancer skill levels then what you have is an amazingly powerful wand if you create a skelemancer and a fairly useless wand otherwise. Is there are a comparable way in D3 for equipment to impact builds and specializations? I did not see it in the beta on item 'drops' up to level 29. In D2, item/build synergies start at level 1. So far as I can tell from D3, I should be able to dump my equipment from my wizard right onto my witchdoctor and have it be just about as effective. That's seems kind of strange. Again, I assume I'm just missing something? A lot of the fun in D2 was picking up some strange item and creating a new character around it. In D3 I just handed my strongest 2-h weapon straight from my barb to my witch doctor, and it worked just as well. That's neat, but it left very little excitement when it came to getting items which is ultimately what Diablo is all about.
I enjoyed playing D3, but I'm just not really seeing the massive customization some others are. If I did I would be buying this on day 1, but as is I don't expect to be coming back to this game over and over again so I'm going to wait for the price to drop and launch bugs/balance issues to be ironed out before I pick up a key so I can try to get the best possible experience when I do play through it.