No, the Avengers is the "crossover" event, though it is more like the usual Avengers book. The "solo" franchises are just like comics. Characters crossover all the time. It will be the same with the Star Wars spin offs.
Yep. Some characters may cross-over but an Iron Man movie will always be about Iron Man and his supporting characters and Thor about Thor and his supporting characters. Individual series of movies a.k.a Franchises
Okay so name some separate franchises with intersecting stories, characters or details.
Yes, some of the solo movies have self contained stories but often they have details and characters that appear or impact other MCU films.
Seperate franchises don't share the same characters or story arc.
We get Loki's origin in Thor, his failed attempt to conquer Earth in Avengers and Loki's release from prison in Thor 2.
In Cap 1 we get the origin of SHIELD, Captain Americs, and the tesseract. In Avengers we get a modern update of all three. In Cap 2 we see the fall of SHIELD.
Iron Man 2 introduces major SHIELD characters, Avengers shows SHIELD help organize the superhero team, Iron Man 3 shows Tony Stark shell shocked from the events of Avengers.
Black Widow has appeared in Iron Man solo movies and Captain America solo movies. Nick Fury has appeared in Iron Man solo movies and the Agent of SHIELD tv show.
Thanos will like play a bigger role in solo movies moving closer to Avengers 3 as a mastermind behind the scenes.
These characters are connected, they share the same continuity, they visit each other's movies and their smaller stories are part of a larger picture.
Separate franchises do none of those things.