It's likely that independent Marvel of the mid-aughts could more easily conceptualize and carry out a movie universe than Disney-owned Marvel could have.

Let's assume the birth of Marvel Studios played out something like like this:

- they realized that even without their bread and butter properties in Spider-Man and Wolverine, they still had a bevy of characters with huge potential

- they got enough of the creatives in the company to buy in to the
concept

- they set up a movie studio and made their vision concrete

- they found a distributor

- they cast Downey (every bit as crucial as the other parts. Fair to assume IM1 isn't as good and this ship may never even leave port without him in the role)


By Avengers 1 when Disney buys Marvel, there's a proven model in place and Disney has, for the most part, bought into that model and limited their interference. Disney's thinking "these movies make a shit ton of money not just because they're about superheroes, they make money because they're good so why mess with it?"

But let's say Disney owned Marvel at the onset of the MCU. Well for one it probably doesn't move as nimbly as it did and still does.
And it's probably harder to green light an entire fleet of films all working toward a big "event" type movie like Avengers. Maybe Disney commits to a handful of Marvel pitches on a trial basis, but it's fair to assume they lead with a more obvious property like Cap or a new Hulk. Those characters have proven to be great onscreen, but they're not remotely as interesting as Downey's Stark was the first time you saw Iron Man 1, and at the time Downey himself was even a gamble, one that the Mouse may not have been as comfortable taking.

So there's a simple moral here; let the storytellers tell the stories and get the fuck out of the way. Decision makers at a big studio have one agenda - make money. But the creatives have an entirely different agenda and that's simply to spin yarns. The reason Marvel Studios right today has worked so well is because the concept of a "Marvel Cinematic Universe" started with creatives and it worked, in turn leading to the suits buying in and (mostly) continuing to allow the creatives to steer the ship. (THERE'S A BLACK PANTHER MOVIE COMING!)

Conversely, it's why these DC movies are so bad, because Geoff Johns is the only dude representing the storytellers and the rest of the parties involved are Hollywood jagoffs who think they know better but have no reverence for the source material. And I like that these guys are sweating right now. I like the idea that you can't just hastily put two commodities together and expect to make a billion dollars, that's when you end up with "Best of Both Worlds" and not "Watch the Throne."

Even though they're owned by Disney, even though there's billions of dollars at stake, and even though they are a very different entity than they were at their inception, Marvel Studios' ethos mostly remains the same; be patient and try to make dope shit. You stick to those principals and more often than not you'll hit.