I agree that Spidey has always been able to sustain his own setting and some of his best stories are on his own. What I disagree with in regards to what some are saying is that they think he should only have that setting. I mean, why purposefully limit yourself? It can go a long way to have outside elements going in, and vice-versa. It was very real issue for The Amazing Spider-Man writers trying to make a cinematic universe when they only had Spider-Man properties to work with.
I mean, even Spider-Man PS4 stuck primarily to the Spider-Man corner of the MU, yet it was very clearly set in a world where other superheroes existed. There was Avengers Tower, Alias Investigations, a Wakanda embassy, Nelson & Murdock, the Sanctum Sanctorum, the Raft (confirming the existence of S.H.I.E.L.D.), Roxxon, Damage Control, a statue of Lockjaw, and of course Taskmaster makes a welcome appearance where he mentions going toe-to-toe with the Avengers in the past. The only elements absent were Fantastic Four and X-Men, due to executive meddling at the time, but that eventually got worked out and we have FF suits and I expect X-Men stuff to appear in the sequel.
The bottom line is that Spider-Man PS4 was great with its own mythos, but the fact that it was connected to a larger world just made it all the sweeter as it made the world feel like its own, and it opens up more possibilities for later installments to expand upon. It was cool that Spidey wasn't the only hero of his setting, even if a lot of it is window-dressing at the moment. I do believe the sequels will further connect Spidey to the larger world, and it's great to have the option to begin with (assuming Sony's MCU divorce doesn't hamper things of course).
I guess I'm trying to say that Spidey and his mythos is fascinating on his own, but adding outside elements in, or bringing Spidey elements elsewhere, just makes it better. I definitely get you saying Spidey isn't as reliant on the shared universe, though.