Personas are useful for developing a general character that you can refer to. But you still have to be able to say "Alice Robertson, who is a demand-gen marketer at $CUSTOMER, is a prime example of this persona and someone we should talk to during product research." If you can't speak to an actual human and validate your ideas, then you are at risk of creating a fake persona who sounds just plausible enough to convince you to make wrong decisions.
Personas are useful for developing a general character that you can refer to. But you still have to be able to say "Alice Robertson, who is a demand-gen marketer at $CUSTOMER, is a prime example of this persona and someone we should talk to during product research." If you can't speak to an actual human and validate your ideas, then you are at risk of creating a fake persona who sounds just plausible enough to convince you to make wrong decisions.