That's very similar to my thoughts on the game...
While the technical aspects were wonderful, the graphics looked good, the level design wasn't bad, but that "consoleitis" it suffered from —talking about those window transitions and quick-timey sequences to get through to another part of the map— were some of the things that take what's good about it and just drags it back down into mediocrity.
I couldn't stand Garrett, with his Goth-y eyes and makeup —I guess he was supposed to have some face-black on to make him more stealthy— but the characters were just terrible: Erin, the Sheriff of Nottingham stumping around and being a pompous ass, then that guy in the alley way selling stuff "for all your nefarious needs" — I mean, WHAT??!! The F?
And like you said, you had to cross back and forth over the same sections so much, and there was always that one spot that you got stuck on getting around 3 or 4 guards that were always watching each other... And taking them out only had them respawning again when you loaded back into that level.
It looks great in 4k and all the features enabled, and they put in difficulty customization, but those boxy levels where you couldn't lean out of a window and take potshots at a guard on the street because "it's in a different zone" is just so immersion-breaking. Thank goodness you can hex-edit the dark shroud and flashy-light explosion when entering and exiting shadows, or it just wouldn't be playable for me. At least it's a decent game with everything tweaked.
But overall, it was just a passing game, just above a Neutral score for me. I played it right after release back in 2014, twice through. Then I uninstalled it, and just recently tried to play through it again here at the beginning of the month, and it took me about 3 chapters to realize that I couldn't continue it — that I still love Thief Gold and The Metal Age SO much more. With all the HD mods and Sound Enhancement Packs, and NewDark, TFixes.. they're even BETTER than I remember.