at least it "feels" a bit like that 1980's Games Workshop game I had on ZX Spectrum.
Ha, I grew up on ZX Spectrum, too... learned how to program on its rubber keys :).
That's why I haven't heard of Dishonored, most likely. 2012 release? It's just starting to come into my "look it up, see if it was actually any good, set aside a few quid on Steam" considerations. Wouldn't be able to play it without thinking of Shadow Warrior, most likely, or even Thief.
I don't know, that argument doesn't work for me. It's like saying that you can't play Quake without thinking of Wolfenstein?
Dishonored mechanics will obviously be very much based on previous first-person games, but with its own twists and additions, and has a very interesting story. That makes it a good game -- it doesn't have to be a groundbreaking original work that has never been seen before. There hasn't been anything like that since.... well, Wolfenstein, probably.
You can say that pretty much every first-person game that's got a story and character development reminds you of Ultima Underworld, and miss out on a lot of really good stuff. Just because modern game designers churn out a lot of worthless crap, it doesn't mean that there aren't a lot of really good things available, too. It's just like movie, TV, and music industries.