You can see both sides of it but I think Spider-Man being part of the MCU would've been all but guaranteed continued success. Spider-Man: Homecoming was the 2nd reboot of the character and it's connection to the MCU is a huge factor in getting fans and critics excited about Spider-Man movies again. The Amazing Spider-Man and Amazing Spider-Man 2 made a lot of money but the movies just weren't nearly as good as the first trilogy in the eyes of both fans and critics. Before the MCU involvement, Spider-Man was floundering.

To be honest, I'm kinda over Spider-Man. Not that these latest movies haven't been really good and I think Tom Holland's been great in the role, but Spider-Man as a character, is so massively overexposed that he's on a similar level as Superman and Batman. Plus, the MCU has all kinds of potentially interesting and fresh stuff going on with the Blade reboot, the Shang-Chi film, Black Widow, the Eternals and a few other things going around.