I follow you up until you conclude that priors cannot be correct or incorrect. An agent with more accurate priors will converge toward the actual answer more quickly - I'll grant that's not a binary distinction, but it's a useful one.
If you are an agent with "less accurate prior", then you won't be able to recognize a "more accurate prior" as a better one. You are trying to look at the situation from the outside, but it's not possible where we discuss your own decision-making algorithms.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.