Andy Serkis provided the only real fun in the movie.
Humor is a big part of Marvel's successful formula, it adds fun to the adventure and a change of pace that gives dramatic scenes more imoact.
So why make this film so dour?
Ain't it the truth!
A big part of Marvel's formula for success is including humor and plain old fun. Which are markedly absent here, except for Serkis's little scene.
They brought the character back for "Black Panther", so I guess we aren't the only ones who liked him.