What makes this all so fun is how you can really do anything with these characters at this point ^.^
Goku is shown to be susceptible to everything from viruses to wishes, mind controlled allies, parallel evil versions of himself, and so on and so forth.
Both worlds contain characters who are constantly monitoring the timeline too. And the Marvel characters are generally way closer to the center of power in their universe... like true gods.... than the Z-Fighters are. When it came to negotiations offhand, wouldnt the fictional deities of Dragon Ball Z world be more likely to sacrifice the Z fighters than Marvels gods would the Avengers.......? Heck, send them all to the afterlife again. Someone will wish them back eventually. Lol
With Marvel, its not so simple. The Avengers are basically holding all of the universes together.
Its mythological, dude.
Goku is like, a weird monkey alien kid at the end of the day, with parallels to journey to the west. Hes the one of the strongest fighters in the universe, but does reality need him to exist in his story?
Without Goku, 11 of the 12 universes would have been erased from existence. Granted, he's the one who put them all at risk in the first place by suggesting it to Zeno, who is the god of the multiverse. So... yeah your whole point is kind of untrue.