I briefly played Hollow Knight at my sister's place a couple years ago, using my now-brother-in-law's console. The game, I think, is not one you can get a great feel for in a half-hour session when you feel very conscious of the fact that you're a guest in someone's house.
I had apparently gotten the game long ago for free from Playstation Plus, knowing its reputation as one of the great indie games of the past ten years.
Anyway, I've now put significant time into it.
Any comparisons you'd be tempted to make to the Metroid series, particularly Super Metroid, would, I think, be pretty apt. You arrive at a desolate village with a well that leads down into a series of caverns, but the caverns branch out to make an enormous, labyrinthine world.
Unlike Super Metroid, or its recent successor, Metroid Dread, Hollow Knight does have some more modern gameplay ideas, including a fast-travel system (notably one that still requires you to trek to your nearest fast-travel location, so it's not like you can just nope out of a scenario if you get lost). There is also a Souls-like element with Geo, the currency you collect around the world, usually getting a handful from each enemy you defeat. Dying, among other things, causes you to drop your Geo, and you have one opportunity to regain it before it's lost and you have to start your collection from scratch.
Like in Soulslike games, this incentivizes spending that cash as soon as you can, though it can be frustrating when you have just shy of the amount you need to unlock, say, an elevator, and then die while collecting more of it. The amount dropped by foes does seem to go up as you get into more difficult areas, but it's a real pressure.
Power progression is de-emphasized even from Metroid levels. Playing for several hours, I've only gotten one health upgrade and only the first fragment of a Soul upgrade (we'll get to what that means). I did get my sword - sorry, not sword, nail, because we're a little bug-person - upgraded, which I actually wasn't sure was going to happen. With rare exceptions, every enemy's attacks only deal one "mask" of damage (the units that your health is measured in) and only recently have I started encountering non-boss/mini-boss monsters that take more than three or four hits to take down (which then got reduced to around that number thanks to my weapon upgrade).
Hitting enemies will build a resource called Soul. The primary use for this, as I see it, is to heal yourself. A full soul meter will have enough to recover three of your masks, of which you start off with 5. Thus, you're going to need to take the fight to your enemies to heal yourself, which of course puts you at risk of losing more health. Healing requires you to concentrate on pouring soul into it, and if you're interrupted, the soul you've spent is still expended even if you didn't get to heal.
This is easier to manage when fighting regular enemies in the world, but against aggressive bosses, it seems like the intent is for you to just get better at dodging their attacks.
Dying causes you to leave a ghostly apparition in the room where you bit it, and you'll need to fight this ghost to get your Geo back. The ghost can hurt you, so it's technically possible for you to die to your own ghost.
In addition to dropping your Geo, though, you also have a fractured soul vessel, meaning you can only store up to about 2/3 of the Soul you can normally. This also means that if you just give up and leave your ghost somewhere, you're going to be fighting at reduced strength (though I suppose if you die again and permanently lose all that geo, your ghost will relocate to the new spot, which might be less of a pain to get to).
The game is hard, requiring some really precise platforming, sometimes forcing you to execute complex maneuvers like striking some bouncy fungus to get some air, dashing to a wall and hopping between spikes. The bosses can be very tough, too. And the runs back can... to be frank, get a little tedious.
One thing I really appreciated in Elden Ring was that, unlike basically all the Soulsborne games before it, most bosses had either a Site of Grace (bonfire) right before the boss room or at least had a Stake of Merika nearby that would let you respawn nearby (though in the latter case, not access the various things you could do at a Site of Grace). It meant, essentially, that once you had gotten to the boss, the game was only really concerned with whether you could handle the boss, and not the big run-up to the boss. It also saved time.
I honestly think a big reason I gave up on Dark Souls was that the run back to Ornstein and Smough was just so tedious. I knew I could fight the things in there, but probably not without losing a precious Estus Flask charge or two. I was nervous enough about the boss itself that I'd make mistakes running to them, and that just made it harder for me to actually beat them.
There's a little of that here - some bosses are buried deep in dangerous territory - I didn't realize the Mantis Elders were something I could come back to later, so I spent a long time running back through their village (where I had opened a bunch of shortcuts, but it was still a lot, especially because I had to stop and fight my ghost there) and showing up for what I can only assume is a super-tough fight with like one or two health, and getting almost instantly destroyed.
I know that this frustration is just part of the difficulty, but it is something I'm struggling with.
Now, art-wise, the game is really interesting. It's both creepy and cute - the fact that all the characters are some kind of bug-person is a nice unifying aesthetic, and the music and art style are both charming. It also means that when they want to get creepy with it, it can get real freaking creepy (I've stumbled into a waterway area - where I am struggling to even find the map - with worm-creatures that split into two separate creatures when you kill them, each attacking in different ways. It's nasty.
While not quite Dark Souls level of bleak, the world of the game does seem pretty bleak, with the caverns leading toward a ruined civilization - one that claims to be the only civilization that ever existed.
This game does not hold your hand when it comes to lore, but I suspect that there's some interesting stuff there if you take the time to synthesize it all. For one thing, I only just found a monument to the Hollow Knight, after thinking that that was my character all this time (or maybe they both are?)