I feel those characters, like the horror guys like Dracula and Franky, don't really fit with the Marvel display given they are licensed characters that have their own story outside of Marvel. I know they did some crossovers but it seems weird to me, like if they had a comic where WWII Captain America meet Indiana Jones, that doesn't mean Indiana goes on my Marvel shelf.
I respect your thoughts on the matter, but I see it differently. I have a Golden Age shelf that has the Justice Society, the few Invaders that Hasbro has made so far, World War II Logan, a DC Direct Sgt. Rock, the Universal Monsters and ... The Rocketeer and Indiana Jones.
God willing and I live long enough to see it happen, they'll be joined someday by the rest of the Inavders, Doc Savage, the Shadow, the Green Hornet and Kato, Flash Gordon, Fu Manchu, Tarzan, The Spirit, The Spider, Buck Rogers, Mandrake the Magician, Dick Tracy, The Phantom, Justice Inc, the Black Cat, Captain Midnight, Miss Fury and maybe one or two others I'm forgetting.
You can blame Stan Lee. When the Fantastic Four, the Hulk and Spider-Man proved to be hits, he started thinking about the direction he wanted his newly formed superhero line to go in. He looked at DC Comics with their multiple Earths (Earths 1, 2, 3 and 297) and he decided he didn't want that. The idea was that Marvel would be one world and most of the characters would live in New York which is where he was from. Stan wanted all (And I mean ALL) of these characters to exist in the same universe. Millie The Model was at Reed and Sue's wedding. So was Patsy Walker and her best friend Hedy. Patsy as we all know eventually became the Hellcat. If you read teen romance comics from the 1950's, you knew who they were.
When Roy Thomas became Editor in Chief, he took that idea and ran with it. And that is why ... Spider-Man appeared in stories with Dracula, Doc Savage, the son of Fu Manchu and Red Sonja. Conan was a Savage Avenger. That's why Rom and the Micronauts were Marvel characters.
It's how Stan and Roy wanted it, and I'm not going to argue with Stan and Roy.
It's interesting that Disney owns the rights to Marvel, Indiana Jones and the Rocketeer. A crossover set during the Golden Age would be a lot of fun.