Why bother? In depth critique is time consuming, if you want to do it right. Kinda like art itself is.
I just pointed out some of the most basic, surface level problems, and the response was in as many words, 'go pound sand'. I'm not going to put in that additional time and effort for someone who's response to criticism is complete dismissal of it. That's what the whole 'oh, well show us your game' bullshit is, a cop out by someone not actually interested in discourse or critique.
I could also dust off my old Wacom tablet, fire up GIMP, spend time to find or create good reference material, and do a fucking bang up job of drawing 2 people on the back of a motorcycle. And if I wanted to do it right, to be able to create something that I wouldn't be embarrassed to claim credit for, I'd have easily spent a dozen hours or more. For what? An outline sketch of 2 people on the back of a bike, but done with good perspective, proportions, an interesting POV; and the dev's wouldn't learn anything even if they wanted to. I could accomplish the same thing by just showing them a photo of 2 people on the back of a bike. Whereas I could do an in-depth breakdown of what is wrong, and how to fix it, for a few dozen art pieces in the same amount of time. Information that was crafted to the specific problems and examples, that a receptive artist could use to actually improve their craft. You know, something that could actually help someone who actually cared.
As far as the artist goes, why spend that extra time and effort if the person hiring you (the dev) is happy with the crap you can shove out in a fraction of the time? Kudos to the artist, they found someone to happily buy and defend their sub-par work. Great gig if you can get it, I guess. Me? I'd be too embarrassed to turn in artwork when I was in high school that messed up basic perspective and human anatomy the way this art does. My high school art teacher would have grilled me savagely if I had handed in stuff at this level. But, it's not my job to fix it.