I have no problem with the game "not taking itself seriously". If anything I always defended the previous one from people criticizing it for "not being serious enough", by pointing that the story was at its weakest exactly when it tried to take a turn for the dramatic and its best when it played comedic tropes.
I just don't like the current sneak aesthetically. That's it. I'd prefer to see the characters actually sneaking, rather than having them suddenly replaced by a piece of environment.