Any other games that have a similar vibe to My Summer Car?

Rain World. Fucking struggling with this one.
Animal Well, little easier than rain world.
Tunic.

Urge is a very strange one but kinda fits the bill

I've sunk hundreds upon hundreds of hours in this

I'll second Tunic. It's RTFM the game.

First review on Steam - Negative:

Personally, I find the game just too hard.

Absolutely NOTHING is explained (there isn't even a tutorial), so I can't even figure out how to get rid of, reduce, or avoid the fog in the early game.

There seems to be a story, but since there’s no clear path on how or where to explore, it gets completely lost.

The enemies simply can’t be fended off during the first fog phase, as they’re just way too strong due to their sheer numbers...

Second review - Positive:

piss

Yup, that's the game I'm looking for!

Neo scavenger might fit the bill. You start out naked in a Detroit that has no regard for the player.

https://store.steampowered.com/app/248860/NEO_Scavenger/

Morrowind kinda does this. Unlike the other Elder Scrolls games that came later, you don't have any quest markers, or anything really to help you find where you're looking for. Most of the quests give directions like, "follow the road south till you get to the fork in the road with a big tree. Go on the eastern branch till you find a cave entrance. If you get attacked by cliff racers you're either on the right path or you went too far. Good luck."

You might dig The Forest.

I died a LOT in the fucking forest.

Raft is kind of like this. You're basically told nothing and you're out at sea on a raft that you can then build with stuff you find.

It was not for me, but almost entirely for the reasons you want a game like this, from what I'm reading.

I don't know why I didn't think of it before, as it's one of my favourite games, but you may well enjoy Oxygen Not Included

So the sequel doesn't scratch the itch, how about Finnish Cottage Simulator it has actually a similar vibe but less focused on cars.

Or some dynastie games like Sengoku Dynasty, Lumberjacks Dynasty, Medieval Dynasty, Wild West Legacy.

Or from your description "unforgivable near hateful to the player but rewarding" you literally describe Dark Souls or souls like games how about Sekiro

Or some hard 2d platformer like Celeste combined with the aboth suggestion you can also try Hollow Knight or Rain World