Very simple: Dragon Age is what makes Dragon Age special. It is an original IP, and not simply playing in someone else's toy box.
I found combat fine, in fact this is the first time I've enjoyed playing a mage. The menus worked well, so I don't understand the complaint about being counterintutitive.
You can't compare the combat systems of DAI and Witcher at all. One is party based combat using skills mapped to keyboard/controller buttons, the other is single combatant based where most combat skills trigger based on a sequence of buttons, ala SoM. It's a different design philosophy.
As for lack of variety in classes? As compared to what? Not the Witcher certainly. We have the same three classes that have been in every DA game. Numerically we have one less specialization than either DAO or DA2, but the specializations in DAI are superior to Origins in that fact DAI specializations give a great deal more than an Origins specialization.
Assassin in Origins has 3 passive skills and one active.
Same specialization in DAI has 3 actives, each with two togglable upgrades, and 4 passives.
Templar in DAO has 2 passive 2 active.
Templar in DAI: 3 active, each with upgrades and 4 passive.
And that doesn't even get into focus skills.
And yes, I'm not including Awakenings as it's practically a new game in and of itself. You can't start a completely new character and just play Trespasser unlike Awakenings were you can or,if you did the US in Origins, have to.
Some people like their echo chambers
I compare it to other BioWare games.
Dragon Age is not even close about beeing new thing in gaming. All the things we have are already part of Neverwinter Nights - some more complex others just basic stuff compared to Dragon Age. NWN was more complex and hard to learn for beginners and DA:O was a nice compromise in this regard.
DA:O combat system is basically an easy version of NWN, which is based on p&n DnD. However it is true that DA:O uses it's own set of rules and not the D&D stuff. Still doesn't change the fact that they are similiar. (not talking about the acutal rules, more like about the amount of stuff, like class combinations, xp loss, how effects are applied and such.)
I don't hype NWN. It was an epic journey, especially with the addons, but also had it's flaws.
DA:I :Freezing characters, fancy hitbox a la bears with 180° hits, always 4v1-10 fights, lack of variety in skills (arguable), tactial view tends to bug around - you can't even move a hill straight up with it, completly let down regarding AI tactics and the battle setting is basically always the same - which was sometimes also poorly done in the other two.
The combination of bugs with a new combat system and some unnessacry simplifications is just too much of a disappointment for me to actually enjoy the battles. They kind of improved it for the worse. I don't want to argue that the mechanic is bad - tanking was never such fun -, but it is poorly executed.
About menu:
PC: The menu is slow, if you move the mouse over an item and take it to thepart of the inventory which to sell it the tooltip will not update automatically. To put it another way, if you sell a certain item, the next item in the list will still have the tooltip of the sold item.
Class:
We have basically the same three classes with more or less the same specializations (knight en. is an arcane warrior). I don't see any improvement in this aspect of the game. The point about having the option to do 2 specs is about individualize ones character. The game simply lacks that. I don't even want to compare it to NWN because this would be an unfair battle. The aim of DA should not be NWN, but again DA:I simply lacks variety. People, including me, expect more from the third part of the series.
Obviously having more than 1 specs would not make much sense in DA:I since we only have 8 slots hence only one spec and with one only one spec there is no need for more than 8 slots and etc.. Somehwat of a circular argument.
Edit: Even though I don't like to say it, but Dragon Age Inquisition feels somewhat console like. I don't hate those since I know and play both worlds but maybe BioWare/EA should just decicde for one side and that's it. That the old ways still work have shown games like Divinity: Original Sin - the kickstarter for the second went great - and Pillars of Eternity.