The existence of the concept of a perfect thing is so obvious as to be pointless to argue...and arguing about the existence of perfect things themselves is pointless because perfection is, as you acknowledge ("based on some specified criteria for judgment") entirely subjective.
It might be impossible or nearly so to argue definitively for any answer being the perfect answer, but "perfect" is no longer subjective once you've established a clear context, an objective criteria for judgment. But that's why there are infinite forms and not a singular form that represents some sort of supreme perfection outside of any context. We might be arguing over the "perfect pill". You want a pill to cure your great-aunt's cancer and I want one that cures erections lasting more then four hours. My perfect pill would be different from your perfect pill. Perfect wouldn't exist in reality but you could have a discussion comparing objectively measurable things in the context of a specific purpose or purposes for the thing in question.
And "Just because you can't sense something directly, doesn't mean you can't come to a reasonable conclusion about it's existence" is the straw man argument used for every form of pseudoscience and new age bullshit that has ever been promoted.
You're reading things into it that I didn't say. I think you're confusing my statements with the fallacy of shifting the burden of proof to the non-believer. Like, prove that God doesn't exist. That's not what I'm saying. My point is simply that there can be plenty of valid evidence for something other than directly sensing it. Most of our knowledge of sub atomic things is based on indirect experimentation. We acknowledge the existence of a black hole by observing the behavior of things around it, the absence of light. Sometimes the reasonable conclusion based on evidence is that something likely does not exist and sometimes the evidence leads us to the reasonable conclusion that something likely does exist. Direct sensing is not the only valid evidence for the existence of something.
The existence of the bear in the previous example was a
reasonable conclusion based on the indirect evidence, IMHO. The existence of a bear seems likely. On the other hand, I have not seen anyone give any evidence for a supreme being, or ghosts, or psychic powers, for instance, that would lead me to think that the existence of those things is a
reasonable conclusion. The existence of those things seems at best extremely unlikely, and there are actually arguments against a supreme being/creator of the universe on the basis of logic alone that makes it seem impossible, IMHO, at least until some paradoxes are resolved to my satisfaction.