I can't agree with that. Spider-man has some of the most iconic supporting characters in comics.
MJ? She helps drive Peter's personal narrative, provides love and support and is about to star in her own mini-series. She is far from replaceable, as the whole mess since OMD (I am SO sorry for bringing it up) has proved.
Aunt May was one of Peter's main motivations in the early Spider-man issues (WAY before Uncle Ben's death had to be mentioned in every issue), he was either trying to help her pay the bills (hence his job at the Bugle), or worrying about her many vague conditions which caused stress and thus drama for our hero.
Actually, without supporting characters who would Spider-man even fight? Are each and every one of his enemies replaceable? They tried, like, 300 goblins before finally caving and bringing Norman back as Spidey's big bad.