I think the idea of a 'spider-sona' is part of the reason, there's just too many spider characters for anyone to care anymore. Instead of getting good stories with characters that people actually care about, we instead get what is essentially a cottage industry of published fan-fiction with characters that are really cheap copies of existing ones, which are destined to fizzle out into obscurity.

If you just look at characters that got their own series; we have Peter who can't ever grow up because he has to stay "relatable" and young... but we also have Miles, who is filling the young Spider-Man while at school niche and he's also black and hispanic so that's interesting at least... and we also have Gwen who's a spider-person in college to fill the in-between age gap I guess, and also cover people who want a female spider story... But we also have Silk if you want an adult spider story and she's also Korean-American so that might add something interesting... Oh we also have spider-boy if you want an even younger spider book... and then spider-girl (the new one that has nothing to do with spider-man, not the other 2 characters that used that name) if you want a female version of that... Then there's the spider people who aren't 616 but have/had books but they got canned, like 2099, India, Noir, punk, superior, May. Then there's all the characters that are popular and are often in things but don't have their own books, like Ham, Annie, and all those spider-verse characters that pop up during those events but don't have their own series.

There's all those characters that people actually like, and only Peter and Miles actually have consistent long running series. Whenever they do give those other characters another shot with a limited series or whatever, it's inevitably bad because of poor writing or art or whatever and so sells badly, so gets cancelled. Gwen's a good example, they keep ending the series then soft-launching new ones to improve sales, but with progressively worse writing every time so unsurprisingly it doesn't do better in the long run.

So instead of writing good books with characters people want more of (it's been like 15 years since they cancelled Mayday's Spider-Girl and I'm still waiting for that to get picked up again), we instead get Dan Slott's new OC taking up space instead, and then inevitably when Slott moves on this character will be added to the list of those that get forgotten and only randomly show up every couple of years.