Movies and TV Shows

So a couple of points...

Marvel has really felt like it's lost it's vision since Endgame. Everything from Iron Man forward had been building to that point and once they hit it, it's like they forgot what they were doing.

The current big bad didn't get introduced until Loki, a Disney+ show, and if you look at the properties:

Endgame - 4/26/2019
Spider-Man: Far From Home - 7/2/2019
Wandavision - 1/15/21
Falcon and Winter Soldier - 3/19/21
Loki - 6/9/21

That's a full 2 year gap and three properties before anyone gets a sense of where the next phase is going. Then:

Black Widow - 7/9/21 (unrelated flashback)
What If? - 8/11/21 (unrelated)
Shang Chi - 9/3/21 (unrelated)
Eternals - 11/5/21 (unrelated)
Hawkeye - 11/24/21 (unrelated)
Spider-Man: No Way Home - 12/17/21

Using Spider-Man to crack open the multiverse first announced in Loki 6 months previously was a good idea, but there was no mention of Kang or what threat he represented. There were also FIVE unrelated properties between Loki and Spider-Man making it easy to forget Kang was even a thing, assuming people even caught the Disney+ show in the first place.

Moon Knight - 3/30/22 (unrelated)
Doctor Strange: Multiverse of Madness - 5/6/2022

A direct follow on what was done with Spider-Man, 5 months later, again, no reference to Kang.

Ms. Marvel - 6/8/22 (unrelated)
Thor: Love and Thunder - 7/8/22 (unrelated)
She-Hulk - 8/18/22 (unrelated)
Werewolf By Night - 10/7/22 (unrelated)
Wakanda Forever - 11/11/22 (unrelated)
Guardians Holiday Special - 11/25/22 (unrelated)

Phase 5:
Quantumania - 2/17/23

First film in Phase 5 makes it clear (finally) that Kang is the next big bad, almost 2 years after the character was introduced in a TV show, but it's not the years that were the problem...

It was the hours of unrelated content spread across 11 movies and TV shows, 14 if you count What If, Spider-Man and Doctor Strange hitting the multiverse angle but failing to mention Kang.

Guardians of the Galaxy 3 - 5/5/23 (unrelated)
Secret Invasion - 6/21/23 (unrelated)
Loki Season 2 - 10/5/23
Marvels - 11/10/23 (unrelated)

And here we are... ~~I haven't actually seen Marvels yet, so I don't know how it fits in to the overall plot.~~ Alternate universe hole. No Kang. I've heard rumors of an X-Men stinger similar to what they did with Xavier and Reed Richards in Doctor Strange.

2 and a half years of churning out unrelated properties after having three phases of tightly integrated continuity is NOT how you keep your existing audience.

So all of that being point 1.

Point 2 is this... In the comics nobody really cared about Carol Danvers. She didn't become interesting until the modern Captain Marvel reboot in 2012. In fact, they replaced her a couple of times. Before that, her major story arc was getting her powers stolen by Rogue who would later join the X-Men using both her own power stealing mutant abilities and Carol's flight, invulnerability and super strength.