At least as Mozilla exists now, I think it would be much harder for it to become "enshitified".
Preface: IANAL, just going off my best understanding.
The Mozilla Corporation is actually wholly owned by the Mozilla Foundation, a non-profit. Profits that the corporation generates are the property of the Foundation, which falls under all the usual restrictions for spending and reporting that 501.c.3 orgs have. So at least as they exist now, Mozilla's profits cannot be used to enrich executives or investors, which is the driving motivation behind the enshitification cycle.