Ant-Man, Black Panther and Doctor Strange are 10x more popular than Blue Marvel and has appeared in way more memorable stories than Blue Marvel. You can't compare Blue Marvel to them. Blue Marvel still has not been fully integrated into the Marvel U in comics. He still hasn't appeared around many A-listers. He still has not been tested. Meanwhile those three not only have but prior to their films they were solid B-listers. Blue Marvel is barely a C-lister. Again, you can't compare Blue Marvel to Ant-Man, Black Panther and Doctor Strange. Those three are not rookies.
As for your edited part. Monica doesn't need the Ultimates to appear more in the MCU. They can easily add her to the Avengers which would be beneficial as Marvel/Disney now has more strong women of color compared to DC/WB.