I recently rewatched the Indiana Jones movies, and I gotta say, Kingdom of the Crystal Skull is not really all that worse than Temple Of Doom. KOTCS gets a lot of hate for its use of "aliens", annoying side characters and super silly scenes like nuking the fridge, but honestly, Temple Of Doom is just as bad. You have Short Round and Willie, two of the most annoying characters in cinematic history, ridiculous scenes like sailing out of a plane in a lifeboat, and it had magic stones and shit. Indiana Jones movies always had some supernatural or mystical element to them, so the interdimensional aliens in Crystal Skull aren't that bad.
Granted, Crystal Skull was worse in terms of silly content quantity-wise, and overuse of CGI to add cute gophers and monkeys and stuff, but in general I don't think it deserves all the hate. Well, it deserves as much hate as Temple Of Doom, really.