dull and overly serious
turgid - tedious
The word ‘turgid’ was originally used to refer to something swollen or distended, like an overflowing river, for example. It has since been adapted to figuratively express something, typically speech, writing, or style, that is overblown and unnecessarily grand or longwinded. The effect of this is to make the thing in question tedious and difficult to understand.
John loves the sound of his own voice and just drones on and on. I don’t think I could stand listening to another one of his turgid speeches.
I employed an experienced editor to review my work in order to ensure that it was free of turgidity and pretentiousness.
The movie started well but then trudged on turgidly for another three hours. The director clearly takes himself far too seriously.