Uh get your facts right man. Sony renegotiated with Marvel to put Spider-Man in the MCU in order to get themselves more money off the property after the Amazing Spider Man 2 severely under-performed and made it clear no one was interested in more films from that reboot, at least enough to make any serious profit off of it. And yeah Marvel is more in charge now of the general story and outline of these movies to fit they're network of films but Sony still gets all the various coins that come from the movie and is in charge of the promotion and marketing and still have the license to do what they want with Spider-Man.It's only a matter of time before that happens, actually. Sony renegotiated the license to put Spider-Man to grant Marvel increasing control over the web-slinger.
What you seem to forget is that when Spider-Man was sold to Sony like 20 years ago Sony not only bought the merchandising and licensing rights but also part of the general character rights as well thus they even get money off the sales of the actual comic books. Since yeah Marvel was not doing well in the late 90's for reasons you can easily look up yourself. Point is though that the only way Marvel would ever get back full control over Spider-Man is if like with FOX, Disney bought Sony outright. Which yeah don't expect that to happen for awhile if ever. Disney was barely able to skate by with it's FOX deal with how much more a percentage that gets them in general entertainment. It's not something they can repeat again as the government isn't going to allow that huge a monopoly in one field, at least again for the time being.
Of course I'm pretty sure Sony is going to make a deal with Marvel to continue having Tom Holland and co in the MCU but they also probably want some crossover elements with their "venom verse" they have full control over that Marvel just has to let them do. That's why Feige said outright that it was Sony's decision for a Spider-Man vs Venom movie: he is just letting us know ahead of time they're the ones who would push for that so whether or not you feel that's a good idea it's not something he has any control of and is just generally warning about. Again Sony is trying to have their cake and eat it too with Spider Man and sadly seems like this is one case where they will succeed unless again there are some pretty major behind the scenes changes which feel pretty unlikely right now.