Homecoming really isn't their movie though. They make the money from it, but a majority of the production decisions were made by Marvel.
I really don't see a scenario in which Marvel, which was negotiating from a position of advantage, would have agreed to a deal in which they can put in work on a character and then have it fucked up by Sony's incompetent spin-offs.
I can, since that's exactly what they did. Spiderman makes money. Marvel Studios can use Spiderman in their movies, and they'll make money. Sony can do their own movies as well and make some more money. Both parties get what they want.
That's why it's called negotiations. Maybe not ideal for the fans, but well, it's how business works.
Right, but having the save Spiderman in both universes will limit what can be done in the MCU films. For example, audiences would notice if an MCU had a Venom origin story given that the character already exists in this universe (as far as most audiences are concerned) and had a heavily marketed solo film. Because of this, there just probably won't be Venom in the MCU, which basically means Sony's Venom is MCU Venom.
Well, yeah. That's what I'm saying. But again, it's not like Sony cares about any of that, and Marvel Studios knew that going in. Everyone on the internet already did.
Officially it won't be MCU, in your head canon it can be (hell anything can be in your headcanon, Planet of the Apes can be a part of your MCU head canon if you want it enough), and for casual audiences it won't make a difference at all. Sony definitely doesn't care enough to just not make the movie - they'd miss out on millions of dollars. And Marvel Studios won't bother using Venom in one of their movies since it'll just add to the confusion. Hell, they can't use Venom anyway without Sony's permission, and Sony already decided they're going to use him in this way.
Consider the tv shows. People involved on the movie side have repeatedly said that chances that the movies will acknowledge them are very, very low. Still, some people consider it a part of the MCU. Officially they are marketed as that. Doesn't make much of a difference in the end.