Yeah I know it would be hated and probably tank in sales. But there are at least a dozen of us that would like it. 

What I mean is a game where if you kill some NPC, do some specific thing, throw away some specific item that you (at the time) consider useless etc you simply can not finish the game AND the game doesn't tell you what specific action it was that made the game unfinishable.

You just do what you do and at some point you reach a part of the game and it can at least be so kind to tell you that because of your previous actions you can't proceed further.

To develop this even further it might even give some weight to "moral" choices, imagen you get the choice to spare or kill a character if you spare that character (that so far in the story hasn't been portrayed as inherently "bad") this has a ripple effect that the character kills some other character that is necessary for progression. Or on the flip side you chose to kill a character that turns out to be key later in the game. It's just that the consequence isn't clear until 15 hours down in the progression. 

Or even you kill (for shits and giggles) an non descriptive NPC, just that you didn't know that that particular NPC would give you a key quest further on. Or even make it more advanced you kill a NPC, but in the back ground the NPC has a story of being friend/spouse etc to some more importan NPC that then does not give you a key quest for killing the first NPC. 

But the important part is that you will not be informed immediately that you made something wrong and when you reach a point in the game where it would matter you are not informed of what you did wrong. 

Yeah I know, as I said earlier, that this wouldn't fly with 98% of gamers. But we are a handful of people that would like this. Of course you would be irritated when you realized you put 5, 10, 15 ,20 hours of playtime into something you can't finish. 

Don't we have the "bad ending" option for that? Making a game unplayable because of a player's mistake seems a very fast way to make the players afraid of doing anything.

Haven't you played any Gothic game?

I suppose you could make a Roguelike around that mechanic, since those are already designed around the player having to restart the game on failure. As for other genres I can't see how it would be a good feature to have, unless maybe if the game is very short. If I play a game like Skyrim and 50 hours in I realise that i did something around the 40 hour mark that made me unable to progress beyond a certain point, I would not touch that game ever again. Even with savescumming such a game would be too annoying to be worth playing.

That's Fallout, New Vegas :p I got in a fail state after following one path of decisions. And had to reload a couple days old save to go a different path!
Same in Alien Isolation, had to reload 2 chapters back and go a different route to be able to continue.
Dark Souls I restarted over 20+ hours in after the game happily let me level myself up into a useless state where I couldn't progress any further without soul crushing grinding to fix the stats I needed to use the weapons to be able to continue.
In Zack and Wiki you could make an early 'mistake' and the game would happily let you carry on breaking your head over a puzzle until you gave up, asked for a hint and got the reply, something you did in your past prevents you from going further, aka restart.

Aren't games like FTL considered RPG? Those are like a game of patience, can always fail depending on early choices and luck.

Anyway, isn't dying considered failure anymore? :)

Not in most RPG since you have a autosave that means you in most cases only lose a couple of minutes of playtime. Death has no consequence. And yes I'm generalizing a lot here since there are always someone that can find the odd game where this isn't the case. 

Also as a design choice I like when games have designated save points that are a bot sparse, because then "death" means more and you become more careful since you know you've progressed a fair bit since the last save (this always with an ability to a one point save if you need to quit the game because of real life). 

Nier Automata has like 20 "bad endings" that work basically as you just described.

dark souls bruh kill all npcs and u will regret ur life was even there in the 1st place haha!

No thanks, I don't mind it on shorter games like Maniac Mansion when I've gotten to a point I couldn't proceed any further. A 50+ hour game no thank you. I was annoyed in Zombi U when I died at the end when a zombie jumped out of nowhere and I got the bad ending.  It didn't help that the game saves immediately after you die, so you have to start the game over if you want to try and get the good ending. 

you mean path of exile?