After GotG they thought they can put any obscure characters on screen and make a billion dollars but its not working anymore without riding the coattails of the
They still could if they hired better writers and gave the CGI artists more time to perfect their craft. You only need to hire people who are extremely passionate about making sure that a specific obscure character looks as good as possible on screen. The passion isn't really there and a lot of these newer acts are being used as placeholders instead of main attractions.
Iron Man was not an A-lister in the 80s and 90s. We all know that X-men and Spiderman were the heavy hitters and that Iron Man was a C-lister before the MCU came around. X-men/Spiderman received all of the cool comics, the cool toys, the cool video games, and the cool movies. Iron Man was elevated to an A-lister thanks to passionate creators and people with a dream and a vision.
If they don't fix their creative issues, it won't matter if the character is deemed as 'A-lister' or not because they will end up screwing over precious favorites like X-men anyway.
Edit: A decent example of this is Shang-Chi. We all know compared to Iron Fist(the character), he is a D-list character. However, while the movie has it's flaws(like the final battle), it felt way more creative and unique because the cast and crew were attempting to do their own thing, tell their own story, and not rely too much on other Marvel elements to carry it. I would put it on the same level as Phase 1 movies like Thor 1, Captain America 1, etc where the movies were a little rough around the edges but still had heart.