its because the avengers (the comic team not the movie) are trash in general...
the reason these movies were made is marvel didn't have the movie rights to the big hitters..spiderman and xmen
there's only so much you can do with c-level characters like black widow and hawkeye, or ...antman

lowkey iron man and cap are trash too, even though RDj did an excellent job portraying tony stark
the characters people give a fukk about are hulk, thor and black panther..but they nuetered hulks power, made thor into a fat clown and didnt give BP any screen time
its good for what it was but lets not pretend..marvel was built on wolverine and spidey.