Just to pontificate for a moment. Not sure if my thoughts are totally organized here.
One of the big divides in SF fiction is Wellsian vs Vernian. In H.G. Well's stories, science is typically seen as the cause of the problems. These stories tend to take a very critical view of the idea of progress and whatnot. The Martians in The War of the World represent science and technology and are defeated, not by science, but by the tiniest of creatures. Vernian fiction, OTOH, tends to be much more optimistic. The protagonists are all men (well, yes, there's that) of science. They solve the problems of the plot through science. The world is made a better place by science.
I wonder if the two sort of general themes might be applied here. A "despair" setting isn't one where things are always bad and are going to get worse, but, rather, a setting where the best you can really hope for is a return to the status quo. A "hope" setting, OTOH, is one where the PC's are capable, and even expected, to make the world better. To change the world (and "world" here can be anything from the very small village to the entire world) in such a way that it's actually better than it was before.
Not sure. I'm just sort of spitballing here and not really making any conclusions. But, it might help to reframe the discussion.
At least for me, much of my exposure to (as you put it) "Wellsian" worlds is that it has to be a world where real change is genuinely impossible....unless it's bad. Bad change is fine. Good change isn't--and anyone who says otherwise is either idiotic, crazy, or lying. Anything good in the world got that way by accident and stays that way only because entropy hasn't gotten around to making that specific bit worse yet.
Conversely, I haven't seen the expectation "oh, we definitely WILL make the world better, we're just finding out
how" in "Vernian" worlds, or at least not the ones I've happened to interact with. What I have seen is the expectation that it is
possible to make the world better, but you might still fail. Good change is inevitable, but only because
change is inevitable. Most change will end up neither mostly good nor mostly bad, but simply different.
If someone goes into a "Vernian" experience believing that good endings are inevitable, sharp black-and-white factions with no ambiguity and no possibility of changing teams, and shallow, borderline-propagandistic presentation, then yeah, I can see why folks wouldn't want that, I wouldn't want it either. But, at least for me, I wouldn't want that because that's a story badly-told, not because "Vernian" worlds naturally have those characteristics.
Perhaps I am overly-harsh on "grimdark" settings. I've just had too many people tell me that hope is stupid and only for babies, while grimdark misery-porn wangst-fests are
mature and
serious and
living in the real world etc., etc. Acting as though that style is immune to the dark mirror of the above: bad endings are inevitable, flat black-and-black factions with no ambiguity and no possibility of forming a new slightly-better team, and shallow, borderline-fetishistic presentation.
Darkness, and grimness, and
realpolitik etc. aren't inherently any more realistic, mature, or intelligent than brightness, optimism, and idealism. Unquenchable darkness, unending grimness, and fatalistic
realpolitik definitely aren't superior. The flaw in both most grimdark as I've been exposed to it,
and most of the "saccharine" things grimdark allegedly was made to defy, is a lack of nuance. Nuance requires contrast and subtlety. You cannot have contrast unless you have some things brightly-lit and other things dimly-lit or even swallowed in darkness. Subtlety is harder to nail down, but "everyone is a terrible person, some just haven't realized that yet" isn't subtle, it's just banal cynicism.