Interesting observation about DA:O...I played through 5 and a half times, though, and never experienced that. Perhaps you would have enjoyed it more on a higher difficulty level. My first playthrough was on Casual, my second on Normal for about the first 20% of the game and Hard for the rest, and all subsequent were on Hard or Impossible.
Also, I know what a hack and slash is. I played D2 for YEARS. The difference is that D2 required some semblence of strategy for the more difficult fights, and potions were a way of life. The same is not true of D3. There is no challenge in D3, no strategy, and no variety.
Path of Exile is perhaps the other extreme...for instance, my Marauder in PoE uses 2H Maces...he really can't use anything BUT 2H maces...but he's really, really good with 2H maces. In Diablo 3, your character can go from 2H weapons to Sword+Board with a trip to town. There is no complexity or variety what so ever in character advancement, which for the last two Diablo games was a huge part of the game. In D1, yeah, every class could get every spell, but it required sacrifices...did you REALLY need to be able to cast Heal on your warrior, cause it would require you to sacrifice points in Strength or Vitality to get the Int to cast it.
The fact that your character development is predetermined and that there are no unique play mechanics in the game at all make Diablo 3 very, very hard to enjoy after the first 20 minutes or so. Every class plays the same way...more than that, though, every "subclass" (and I use the term loosely) plays exactly the same. In Diablo 2, a Frenzy barbarian was a totally different animal from a WW barb. In Diablo 3, every skill is either A) completely worthless, or B) the same as every other skill. You left click on everything and occasionally right click. That's it. Item properties are also pointless...so much so that the only thing that matters is the great big number they plaster on the tooltip (DPS for weapons, Armor for armor). That, and the weapons and armor are so artificially restricted that there's no possible way to use something that might be considered suboptimal for your class. Remember Throwing Barbarians in D2? Useless outside of Normal mode, but still fun to mess around with. No such thing in D3. A barbarian can't even EQUIP a bow.
Anyway, I've been over this. Some people might like that style of gameplay, but I prefer a more rich style of play. Even in a hack-and-slash type of game, I'd like some depth of character and depth of gameplay. Path of Exile perhaps takes the depth of character development a bit too far, and the depth of gameplay perhaps not far enough, but I have to say I prefer that to Diablo 3, which is completely lacking in both categories.