The MCU was ALWAYS built on the "fringes" because all the moderately desirable properties - Spidey, Hulk, X-Men, etc - had been sold off when Marvel was in mega-fire-sale mode. Iron Man and Cap were B-listers at best. The MCU has shown, remarkably, that it can thrive even further out on the fringes, with a blockbuster series based on nobodies like the Guardians and a very successful launch for Shang-Chi.
Honestly, we've heard the same criticisms, the same portents of doom - "oversaturated, losing efficacy, etc." - since almost the moment the MCU began 14 years ago. Box office returns show that they are as accurate now as they ever have been. If the MCU ever gets into real trouble, sure, they can pull the X-Men rip cord. But right now, when you can make money off Shang-Chi, there's no reason to do so.