This is all true.
Additions to your thoughts: Superman is a big problem. He morphed from being about Hulk strength & jumping ability to having unlimited powers, including time travel, and it makes having a compelling story difficult. Batman has been recreated so many times, nobody knows which Batman to use. Zach Snyder has totally screwed the DC Universe, because he makes great visuals, but can't create a story. Watchmen was his best, and he visually followed the comics, almost exactly. When he did Batman vs. Superman, he pulled all the fight scenes from Frank Miller's Dark Knight, and the rest of the incoherent plot was what he came up with to string the fight scenes together.
Marvel had to recreate Spider-man after Sony false started twice.
DC has fallen into the Watchmen/Dark Knight/Snyder trap. They're not trying to recreate the Nolan Batman series, they're going for the uber dark Watchmen stuff. It creates a bigger problem, because the classic DC characters (Batman excepted) tend towards more playfulness than the classic Marvel characters. The Nolan Batman is impossible to transfer to the rest of the DC characters, because in that world, super powers didn't exist. Superman didn't exist. The Flash could be built into a decent character. Believe it or not, so could Green Lantern. The Martian Manhunter has possibilities. Creating a decent movie about Aquaman would be like Stephen Hawking doing a 360 slam dunk.
In addition to having an overarching plot across the movies, Marvel has several characters who never get their own movies, but create a connection between the other movies. Black Widow, Hawkeye, Nick Fury, Falcon, & others, form a glue that keeps the universe cohesive. They also recognized that certain characters, like the Hulk, are too difficult to write a movie around.
Oh, this thread was about Captain Marvel. I'll wait and see. I think Marvel's throwing it out there, and if it hits, she becomes a more significant character. If it bombs, she becomes a background character in the future movies. Captain Marvel has been recreated several times, so it's not like they're risking a significant property.