I'll just say this.
Everyone of experience should have their opinions valued at a certain degree.
However, if you need feedback on how a map plays out, experienced players are definitively a better source than simply experienced mappers.
If they're a combination of the two then it's even better.
Experienced players can certainly find issues in how a map plays out, what's sightreadable etc.
Mappers however are able to make the map look nicer and more appealing, which is a more artsy thing to do but is still a fairly important part of the map. They can also identify what kind of patterns suit the music. Not saying experienced players are not able to do this but this is the "main feature" of an experienced mapper imo.
Also flow is a term that's pretty shit because its subjective. Don't use it unless you're like #50
I'm not putting dirt on anyone, really, but the kind of person we should rely on definitely depends on the situation.
Honestly I think my taiko looks really dumb and shit. It doesn't LOOK fun to play, but it certainly is, and it feels rewarding to FC. That's more important to me!
But everyone knew this already, right??