Spider-Man could pop-up in Marvel's movies and Marvel heroes could be in Spider-Man's movies but everyone kept the rights and most of their individual money from those films. There could be other Sony-hero movies (like, "Venom,") and those could involve Spider-Man too even, but no Marvel Cinematic Universe stuff. It was a unique little set-up, but it seemed to work. It may be falling apart now with Sony and Marvel having a nasty break-up.
I think everyone is probably a victim of their own success. Since the newest Spider-Man first appeared in, "Captain America: Civil War," and the rest of the agreed-upon shared movies have wrapped the Marvel Cinematic Universe movies have gone on to make even more cash, and Sony probably feels emboldened with their own hero-movies thanks to, "Venom," doing incredibly well. Hence, we have two companies butting-heads over who gets how much much money for each other's flicks and any kind of deal to basically, "Share," Spider-Man is possibly quite dead in the water for now. This is awkward as Spider-Man is now so ingrained with some of the Marvel heroes and them popping-up in his movies, it would be awkward for Marvel to try and completely ignore Peter Parker or the next, "Spider-Man," to drop any pretense of the, "Avengers," existing in his world.