Is PoR actually enough after all that has happened so far?

No, I think PoR alone is not enough to gain user trust, did you know that some time ago there was information that stated that various exchanges formed a coalition to lend and borrow funds for PoR purposes? Because of that, PoR alone is not enough, exchanges need to also make their PoL (Proof-of-Liability) reports, with the combination of PoR and PoL, I think it will be enough to gain users' trust.
Aside from this, they must also provide a high quality security on their platform and gives a guaranteed return if the platform got hacked, just like the other site who are paying the money theyve loss from previous hacking incidents. Also, PoR should not be your basis on choosing the exchanges