I was having a conversation with ChatGPT about Daredevil and it recommended a couple runs released after my time as a reader that it thought I might enjoy. It provided, at my request, links to several page samples from the recommended runs. Ultimately, while I enjoyed the work of one of the artists, I found the latter artist's work--at least in the samples I saw--far less satisfying. In my opinion, the latter artist consistently chose unfortunate perspective points which contributed, in part, to the production of a collection of static moments in time. He also seems to produce flattened backgrounds, as if the subject--often appearing static itself--is simply superimposed over indistinct backgrounds with little variation and visual interest, and no illusion of depth. Of course I'm aware that many of my favorite comic book artists from my reading era often produced empty backgrounds, but from my perspective that technique produces an integrating effect rather than a sense of superimposition.

And that brings me to the standard I'm wondering about...is it fair to judge a comic book artist's work by mentally removing the subject of the images and assessing what's left? As I said, it doesn't feel fair to me, but, at least in this case, I can't help but doing so.

That said, I'd like to challenge your suggestion that art is subjective. We tend to treat that suggestion like a truism without ever really pushing back against it, but there do exist enough broad patterns of agreement--across time and culture--that the best agreement I can reach is that judgement of art is subject to a constrained subjectivity.

I think our collective consciousness has been so molded by what is presented as ART from so many fronts, we, as individuals, can not even analysis what is art for ourselves. I just go with what I like and don't worry about it being art, without any expectations of anyone liking what I do. 

I imagine it depends on the artist and style.  Neal Adams used realistic-looking buildings and naturally integrated them with realistic-looking forms.

Alex Maleev's "messy photo" backgrounds fit his "messy photo" forms well.

ARCHIE or SIMPSONS open and clear backgrounds are deceptively simple but quite effective in giving the more cartoony figures a solid world to move through.

A lot of the classic comic book artists occupy the landscape between cartooning and illustrative and the trick is matching the environment to the figures.