I did my degree as a mature student just after your time Soz and I think it was an era of change.
When I started the degree there was a push push push to make work abstract, a constant pressure. As a mature student I went in with maybe a bit more idea of who I was and I was determined to learn everything I could but come out as
me, but a better me.
I watched the kids do abstracts with little meaning to them, muddling through slightly bewildered sometimes, doing process paintings, pouring paint down the canvas one way and they another, trying to please the tutors. At the degree show the first year I was there, I felt like some of them were clones - their paintings were the same, no individuality and I promised myself not to go there.
They would then stand and do a dark angst-y spiel about the work and those of us who were painting seriously (well trying to, with much angst of our own!) used to mutter about it! They could rattle a few pieces off pretty quickly and then talk it up.
The uni inspectors came around and commented on this and with some staff changes as well, things changed. Figurative art gained respect again and there was a really healthy diversity.
Less dark art, more variety altogether.
I did a couple of 'dark' projects myself - partly 'cos I realised the angle would appeal to the tutors

but also because the project
needed it. Other work was landscape/abstracts and about mood along with light, weather,time, colour but not dark at all.
I think art must have something to say, something
sustaining and for
me my interests are mainly light, colour, form, and in the landscape add seasons and time - I like the 'bones' beneath the land in the same way that the bones of the figure are essential.
There are some really really good artists about over here who are certainly not dark, David Prentice, Kurt Jackson, Ross Loveday, Maggi Hambling, Lucian Freud, David Blackburn, Barbara Rae and loads of others. (all worth googling)
I love the work of Kathe Kollowicz but it was about a dark era and the work rightly reflects it. It wasn't dark as in posing gothic 'art' - I love your equating it to junk food jln! I think pretty-pretty paintings are in the same league - Kincaid for instance, pure junk food.
Paula Rego's work is dark and disturbing and there are others but I'd say the bulk of painting isn't - and it covers a wide spectrum of styles, subjects and media, which I find very healthy.
I never did like Duchamp - like a lot of conceptual work now it isn't sustaining - I feel 'ok, I get it ..... and now what?' I certainly have no wish to see it again.