I don’t think you can compare UFO50 and Silksong.

UFO50 is voluntarily retro and purposefully use poor design as a kind of homage to video game progress and as a way to foster nostalgia. Part of the pleasure is seeing the changes between the games pretending to be older and the newer ones. Plus, it’s pretty clear it wasn’t made with the idea that most players would finish all the games. Part of the pleasure is sampling the large collection, closing games you don’t like until you find one that sticks. UFO50 objectively contains games which are not that good next to real gems but it is particularly brillant as a collection. Plus independently of how it plays, it’s interesting in itself as a kind of experience. That’s indie at its best.

Silksong is supposed to be a modern game and excels at some parts but the issue is that some design decisions are just, well, bad. I agree with the person you are replying to that it’s not particularly respectful of its player’s time for exemple forcing you to grind and slog repeatedly through uninteresting parts to actually play the fun parts. This is notably something FromSoft entirely solved a long time ago. To me that’s entirely orthogonal to being difficult. It’s an enjoyable game but a flawed one which makes for a tarnished experience.