Quote - Here's the link that made me question the value of criticisms from artists who aren't as good as the artist that they're critiquing.

The problem here is one I've experienced when I've critiqued writing.

"What gives you the right to say that?  How many published novels have you written?"

The problem is defining "aren't as good as the artist that they're critiquing".   How do you measure that?  And does it include specifics or the whole image?

What I mean by that is assume someone does a beautifully artistic NVIATWAS image and calls it something like "Assyrian Warrior" or whatever and describes it as their impression of a female Assyrian warrior getting ready to go battle the Egyptians or something.

Someone points out that the facial features/skin colour/whatever is wrong.  It's a John Wayne Playing Genghis Khan thing.  Real Assyrians didn't look like that.  Their temples didn't look like that.  Their swords didn't look like that.

Does the artist (and supporters) get to dismiss that criticism just because the person doing it, who might have professional expertise in Assyrian culture, hasn't produced a render of equal quality (or any at all)?

I'm a geologist and a volunteer firefighter/EMT and used to be a soldier.  Now I don't have the skill to direct a big Hollywood movie, nor probably write one, nor do the special effects or the acting or any of the other elements involved, but does that therefore mean that I can't criticize the laughable science in "Volcano", the horrifyingly bad portrayal of firefighting in "Backdraft" or the ridiculousness in any number of war/action movies featuring the circular firing squad or similar weapon-related stupidity ("Total Recall" being a particular offender in that one)?

Same for writing.  Same for art.