Wouldn't that make Frictional Games guilty of "stealing" from the first adventure games?
Or every platformer after Mario bros. guilty of stealing from Mario?
Every shooter after Wolfenstein guilty of plagiarism?
Etc etc etc.?
I'm sure there are games that try to be wannabes but most cases it's just devs using a gameplay style/genre. You don't have to reinvent the wheel for each new game. A massive amount of GOOD (read: GOOD) games use mechanics that have become gaming staples and either polish them to a sheen or add something to it.