It's easy to Monday morning QB this topic. As a dude who was born in the 80s and spent most of my childhood in the 90s and early 2000s, the only superheroes worth talking about were Batman, Superman, Spiderman and the X-Men.
Nobody cared about Iron Man, Thor, Hulk, Black Panther, or Dr. Strange. People knew of them, but there wasn't this need for them. And nobody could've predicted the 10 year Marvel plan that actually ended up being the best thing to happen to comic book superheroes and the superhero genre of movies.