I'm not sure what the question means.

Whether Perplexity is useful to someone, and how useful, will depend on how effective it is in giving answers that are (1) correct as often as possible and (2) checkable if they're sometimes wrong.

If Perplexity's answers often treat AI-generated blogspam as reliable then that will probably make them less often correct (because people generating AI blogspam generally don't need what they generate to be consistently correct) and harder to check (because people generating AI blogspam generally don't need what they have to be clearly sourced, and because even if they did it's an extra step of link-following).

So if Perplexity turns up a lot of AI-generated blogspam, that probably makes it less useful. Is it "up to Perplexity"? Again, I don't know what that means, but I don't see that it matters. What matters is how much value it provides, at what cost in time and money and effort and attention. If its output is mostly repeating claims from AI-generated blogspam and that makes the answer "not much, and at too much", then so much the worse for Perplexity even if there's some sense in which it's under no obligation to do better. If its output is reliable and checkable, then so much the better for Perplexity even if some of its deficiencies are in some sense moral failures.