A lot of it comes down to Slott being vocal in his defense of the company's decision, but yeah even then, it's weird the way people have latched on to singling him out as their target for this.
Part of what I was thinking to is that, in this past decade as well, the way Spider-Man as whole has been marketed has also shifted. The days of the Spider-Man comics just being "Everyman" Peter Parker and his supporting cast is over. It's happened in the comics, with Spider-Man becoming more ingrained with the Avengers, and more Spider-themed spinoff characters (Miles, Spider-Gwen, Silk, etc.) getting launched. You see it in the cartoons, with both Ultimate Spider-Man and the more recent one being a more team/team-up based series. You see it in MCU movie. Slott (and Bendis to a lesser degree) get a lot of heat for the way the "Spider-Man line" has changed. But the thing is, I think that's a thing where even when he steps down, I don't see changing anytime soon.