The only thing more shocking than meeting members of the Earth 838 Illuminati (John Krasinski as Reed Richards, Lashana Lynch as Monica Rambeau’s Captain Marvel, Hayley Atwell as Captain Carter, and Patrick Stewart as Professor X) is to see them all die. This is the MCU we do not see major heroes die like that. They always come back.
But this is also the Multiverse. Just because this Captain Carter or Reed Richards died in this universe does not mean every version is dead. That leads us to believe that, yes, Earth-838 Reed Richards, Captain Carter, and Professor X are all, indeed, dead, but many other versions still remain. The one exception might be Captain Marvel because her death is not as definitive but, she’s still probably dead.