[throwawayAAUGGH]

The original donkey kong is pretty difficult compared to some of the wide-audience games that have been coming out. As far as I can tell, if the audience of a particular franchise includes younger generations as a majority or near-majority, the difficulty plummets. I don't think "plummets" is even that sensational. See pokemon, kingdom hearts, mario games, final fantasy games. Some franchises and genres have survived but not all of them.

I might be missing some other reasons why this could be happening, like increases in game balance and coordination.

Play Mario Odyssey for an hour or two then play Super Mario Bros 1, 2, or 3 as one startling example.

[somenameforme]

That's mostly the MBAification of games that I think is completely disconnected from what most kids want. But the MBA logic is about maximizing market reach. Relatively few people will choose not to play a game because it's too easy, but ostensibly the same isn't true of games that are seen as difficult. Of course Elden Ring, Dark Souls, et al completely proved this to be nonsense (to say nothing of pvp games), but who's gonna let a bit of reality get in the way of pie charts, bar graphs, and powerpoints?

In the world of games outside the big money AAA MBA stuff, there's plenty of highly challenging franchises that maintain true to themselves and thrive, even with plenty of kids playing. E.g. - I suspect the median age for Binding of Isaac is well below the age of consent.