>>110844327The Avengers were just really really accepting of people back then. Literally the first big team shake-up back in the 60's had Cap bringing in Wanda and Quicksilver, the literal children of Magneto alongside Hawkeye, a guy who last time we saw him was henching for the Circus of Crime until Tony pursuaded him that being a good guy was totally sweet.
New York super-criminal Sandman has been an avenger. Moondragon raped the Hulk once, and she still got a shot on the team. Scott Lang, Jocasta, Beast... the Avengers will basically accept ANYBODY if they can give a decent heartfelt one-panel speech about how they should be given a chance.
That's literally all they look for.