Stupid progression is the thing in EVERY one of these games where you get a powerup - sometimes a cool glide or jump ability, sometimes shit like the box pushing in Circle, so keycards I guess - and then you look at the map and wonder which of these twenty dead ends has an obstacle that matches the thing you have, and hit the teleporters.

One of the things I hate the most about games that bill themselves as "metroidvanias" is that they do what you describe just as you describe, where the powerups are always 1:1 with the some kind of obstacle blockings some number of paths. That's why I called it "keycards", because it's "blue keycard opens exactly blue doors, red keycard opens exactly red doors" like in boomer shooters. I hate it because, at that point, just have a linear game! By putting it all in a map like this, all you accomplish is padding the game by forcing the player to backtrack over shit they've already been to, or check a bunch of dead ends if they have a poor memory.

In my opinion, the greatest achievement of Hollow Knights game design is that it mostly avoids this. How do better metroidvanias manage to that? Well, here's a specific example from Aria of Sorrow (as I remember it): Have a gap that you can't cross with just a jump, and make it so both a glide and a double jump are separately accessible, so that the player can stumble on either one, then go back and cross the gap without access to the other! It's only a little less contrived, but it feels so much better and gives the player a lot more freedom to actually explore, justifying the jumbled map design.

Hollow Knight is full of progression gates where you can totally do it with multiple powerups, even if it looks at first like only one specific way is possible. It also has a handful of hard requirements, but makes up for that partially with all the different pathing that is possible.

enemies just get styled upon

Can be a good thing, since that's how DMC operates, and Godhand if I can make that reference.

These games have nothing as cool as the axe knight hallway in Castlevania 1.

I kind of didn't realize that people still like Castlevania 1 for reasons other than nostalgia and good sequels. I'll look into it.

Is Hollow Knight actually good?

Yes, it is one of the better video games and easily the best "kind of Aria of Sorrow-like game" I'm aware of after spending years looking, including beating AoS by a country mile (though I like Souls in AoS and Hollow Knight doesn't have quite the same diversity of nonsense).

Is it not a nightmare to backtrack through twitch platforming and difficult combat?

You said twitch platforming a couple of times and compared it to SMB, but I don't really know where you got that idea. Well, I do know, it's from The Path of Pain, an optional area (with no mechanical reward) that tries to push the player's tools to there limits). I don't think I ever did it. Besides that, the required Royal Palace section probably qualifies as "twitch platforming" but it's only one part of the whole game. As someone with "Kirby player"-level platforming skills (read: I'm not good) I found it pretty frustrating, but I still beat it within a few hours. I think I ended up cheesing it slightly because your attack is really OP for dangerous platforming segments.

The combat is really only difficult when you're stuck somewhere, which happens maybe twice in the game with mandatory mob encounters and then with bosses (though you can even escape the first of those, probably as a Dark Souls reference). Therefore it barely factors into backtracking because you can just run away and the enemies generally aren't fast enough to chase you.

On top of all of this, fast travel gets introduced very early (the game is pretty respectful of your time), and they are usually paired with a savepoint nearby. Given all of this, I think backtracking is a non-issue generally and the more difficult thing is boss runs (i.e. when you die, needing to run through the level to get back to the boss, etc.) because some have a save right before, some don't, and some have a save on a branching path that you might have missed. It still isn't too bad because being a coward is OP for exploration, but it's a factor.

Does that cover your concerns?