DA:I is almost perfectly linear in terms of plot, and perfectly non-linear in terms of location = I can't stand it.
KoTOR is almost perfectly non-linear in terms of plot, and perfectly linear in terms of location = I adore.
What's important here, I think, is that I don't think DAI is linear in terms of plot, because I don't accept the conventional definition of what the plot is.
The story of the game is simply an account of your character's adventure. If there's freedom to craft your own character and his motivations, then the story is largely created by you, even if the actual actions undertaken by your character are severely constrained. The story is even more your creation if the actions of your character are under your control. And that's what I think DAI does.
KotOR succeeds on the first points, yes - you get to craft a blank slate character and control why he does things and how he reacts, but his actual actions are really quite restricted. He'll always complete Taris in largely the same way, with little else to do there. He'll always complete each of Dantooine, Manaan, Tatooine, Kashyyyk, and Korriban in largely the same way, thought the order is mutable. There are some meaningful sidequests on those worlds, though, and they do offer considerable freedom to resolve them as you see fit. But once those are done, and the twist is revealed, the game becomes remarkably linear again, with little to do aside from the critical path. And yes, there are different endings, but the paths to them are very similar except for a bit of dialogue.
DAI surpasses KotOR, I think, because of all of the freedom to do things that may or may not have nothing to do with the critical path. The critical path may as well not be a defined quest line so open is the game. So I don't agree that DAI has a linear story, because there are a great many very different stories you can tell in it. KotOR's stories are all broadly similar, save a very late divergence.
In theory, I actually prefer games that don't have an identifiable critical path until you've progressed much of the way through the game (BG and DA2 both do this well - the only other BioWare games to come close is ME). However, there are many other factors at work, so that alone isn't enough. Also, I really enjoyed the NWN OC, and its story is extremely linear.
As for linear areas, I don't think those are ever acceptable. They're so fundamentally flawed that I can't accept games that use them (KotOR's saving grace is the limited exploration in places like Dantooine and Kashyyyk)