At the minimum it will be on par with a MIG-29M/MIG-35. Suffice to say, that is good enough to pose a strong threat. No doubt it will be inferior to the F-35 but depending on how well the avionics are and how good the stealth aspects are it will give it an edge over F-16s, Super Hornets, Eurofighters and Rafales. Which is what it will compete against.
It will of course be a while until it actually enters production. But I think in markets like Vietnam, India and other Asian countries it may find a spot as those countries aren't getting F-35s within this decade. Vietnam seems to be ordering the Su-57 but at the same time seems to want to become more closely aligned with the US. Depending on the route they choose, maybe they will fly a mixed fleet of Su-57 and Su-75s. Or go with American/European options.