Thief (4) wasn't bad. Yeah it was different in a lot of ways, but that's what happens as technology advances. And it succeeded at being spooky as hell in certain parts.
I also really liked Thief (3): Deadly Shadows, which was pretty much exactly the same to a lesser degree. Major graphics upgrades, and open world, combined with removing some tools and adding others. Damn straight they feel different, they *are* different, but I felt they stayed reasonably close to the setting.
I do hate that they called it Thief instead of Thief 4 though.
It's bad in terms of being a Thief game, i.e. an open sprawling game where the player is free to take whatever route they please, as long as they achieve the objective.
Where you are not assaulted with cutscenes or "cinematic moments", because you are playing a fragile and relatively weak person who is trying to go unseen and avoid all conflict. The guff of the development team to say "We want you to play as a thief, but we don't to force you to play as a thief." Did those blokes read the title of the damn game? If you are going to make a game, don't be a coward and half-ass it.
It's not a case of evolving a game into a new, better direction, it's an example of throwing out all the core concepts of an established franchise to chase after the playerbase for a different game (In this case, Dishonored.)
They didn't want to make a Thief game, they wanted to made a Dishonored game, but also wanted to cash in on the name of a venerated series. Not only that, but it uses the name of Garrett but takes the characterization in the exact opposite direction (I don't care that it's a "prequel".)
It's not a reboot if you show no respect to the franchise you are supposedly rebooting; if they wanted to make a stabby stealth game, they could have just created a new franchise, like what Dishonored did. Don't use a name if you aren't intending on using it properly.
TL;DR: Thi4f is the Tomb Raider 2013 of the series. Both are fine as what they are, which is clones of Dishonored and Uncharted, respectively, but a slap in the face to people who had the gall to expect that a game labeled as something would actually be that thing, instead of a relatively generic high budget rip-off of another popular franchise.