I agree with Pike: Inquisition is a humongous time sink with large areas (yay!) with rather tepid sidequests (boo!). I mean, the Hinterlands is a prime example of that sort of grindy time-sink sort of design that was fun for a while, then you kinda just get bored. The main quests are great, but outside of those, there's less of an opportunity to enjoy rich sidequests with a colourful array of characters. That's what Dragon Age II excelled in.
I also felt that you couldn't do as many dialogue choices in Inquisition either. You can't bribe, lie or talk your way out of things nine times out of ten. Your companions don't chirp up as much during cutscenes, which is disappointing.
I actually liked the gameplay. That was one of the best bits. Maybe provide a bit of variety. I appreciated every companion having their own unique tree, which helped differentiate them from others in their class. But in Inquisition, your specialisations are those unique trees, which lessens the effect.
They're the main things. Still a good game, but it worsens with age (and length of play). From the fourth game, aside from obvious 'good story' and 'good characters', I'd like a more fleshed out array of sidequests, and better customisation options. Especially the hair: my goodness you basically choose from 'shaved', 'slightly less shaved', 'short' or 'weird hairstyle I've never seen before'. Not many long hairstyles.