Bob Iger didn't wake up one morning and decide to make a lot of Marvel movies. Like Scorsese's ideas, Marvel started out small and creatively (by an immigrant's son in New York). The appeal of the themes and characters are the relevant issues. All movies that earn studio support need to be properly sketched out and pitched. The movies that made their way into the Marvel franchise had to play by the same rules as anything else. If Irishman couldn't win major studio support, that's not MCU's fault. Frankly, most of Scorsese's recent films were greenlit because he pitched DiCaprio as the lead to the studios and they banked on him as a teen heartthrob. Otherwise those movies would have been in Netflix's scrap pile too.