He makes some very good and relevant points about that in his video. tl;dr version is subjective opinion != objective fact, someone liking a game you don't doesn't mean they're an idiot, a reboot or sequel being different from the previous game doesn't mean the game fundamentally sucks.
Of course, Thief has plenty of problems even without comparing it to the originals (terrible AI, terrible story, context-sensitive everything, excess linearity and lack of decent exploration, poor level design, poor pacing, technical incompetence and bugs, misleading marketing and gameplay demos prior to release, etc.) which probably just renders it a poor game outright.