Yelena does apparently state that he's controlling the Red Room now (as the MCU version of his normal "train henchmen-for-hire" gig in the comics, I guess).

Well, Boba Fett was intended to be the primary antagonist of Revenge Return of the Jedi before the fallout from Lucas's then-failing marriage caused him to sour on the idea of making further SW movies.

His character concept is literally "guy who can take on all the Avengers at the same time and win." It's probably a fool's hope, but it really would be nice if the film didn't water him down too much. The one time he ever came up against a Black Widow (Yelena) in the comics (while disguised as Deadpool, long story), what transpired was more of a conversational beatdown than anything remotely resembling an evenly-matched fight:



Maybe the technical read-outs on his helmet visor have something to do with it.