Fortnite is something I've grown to appreciate (but never play, because I will never make an Epic Games account). The microtransactions are so silly (I feel bad about humanity and society when I think about them) but the game has a lot of technical depth and variety. There's a Guitar Hero in Fortnite. There's a Minecraft in Fortnite. It's really a lot like Ace of Spades was before Jagex killed it.

What I mean to say is "I think you and I think about games similarly and I read your post with that lens." I think the main contention is that "fair" is necessarily subjective, and tricky to define.

If I were to suggest a definition, I'd say a singleplayer game which feels fair is one communicates well, does not have difficulty which demands a huge time commitment, and (counter-intuitively) has generous hitboxes. E.g. Celeste is fair because everything is clearly communicated (you can see the level and know what will kill you), the tricky levels send you back to the start of the screen, and the hitboxes feel sensible by lying to you up and down. (Celeste has three hitboxes, and hazards have tiny and sparse hitboxes.)

And often these games are not as good as From at realizing what players can take or not.

This is something I really liked about Tunic. I could beat any Soulslike I think, but I usually don't want to put up with that. But I had this experience in Tunic, where the first boss was very difficult. I thought I might have sequence broken to an impossible boss. Then, (spoilers; rot-13, you can use DDG to un-rot13 V unq pbyyrpgrq n cntr bs gur phgr va-tnzr znahny, juvpu unq n oyheel fperrafubg bs gung obff ng ebhtuyl zl fxvyy yriry, jvgu na rapbhentvat "LBH PNA QB VG!" zrffntr. Gur tnzr nagvpvcngrq zl pbaprea naq gbyq zr, npghnyyl, lbh pna orng guvf obff.

Then I beat the boss, and I was able to trust that I could beat any of the bosses in Tunic. They were just about the edge of what I was willing to put up with, though. I liked that experience very very much.