I've seen a game on the PS4 that had like 90% achieved on a trophy that pops when you reach the title screen or click new game, people must install the game boot it up and quit out before the title screen loads lol.

No, you can turn off the notification that you won an achievement/trophy, but you will still get it.

Then my friend's, who I borrowed Uncharted 4 from, playstation is broken, because the system doesn't even know he has the game, let alone has finished it. (He has trophies turned off btw and currently has none according to my friends list.)

Can't comment on Xbox One, don't have it, presumed you could just turn them off.

No idea, he has no trophies whether view from my list, looking at his profile, comparing them, or viewing via here: https://www.playstation.com/en-us/my/public-trophies/

So what you are saying is he has the trophies but they are on his console, and his profile only? No one else can view them. But would those private trophies be recorded for the % stats the original post is trying to point out.

Because they're used to playing games like The Witcher 3?

Bücause... maybe... its not that good.

If anything, this shows that achievements suck for the majority of players. And you can even tell that by looking at people's gamerscore. It was a nice plan to drag people into playing and spending more money but it only works for very few people.
They start a game, realize it's not their cup of tea and quit. That's it. Might even be rented or a copy from a friend so no money wasted.
I got out of the vault in Fallout 3 and quit because it didn't catch me so I'm left with the very first achievements you get for pressing A. Yes, I suck at it, virtually spoken, but actually I just don't like it and don't want to be good at it. There's hundreds of other games I'd rather play and I'm ok with a lame gamerscore in Fallout 3 when I have 200k+ in total.

well there are two types of achievement hunters.

Completionists and people who prefer a high score. Getting only one achievement in a game would be devastating for a completionist but no problem for a high scorer. I don't see how the achievement system as a whole would suck because of that.

Yeah, and I married her.

I actually do that with many games. Start them, play it for a couple of minutes/and hour and than put it away for sometime when I will have more time on my hand. Obviously that never happens in most cases. I have so many games with 0 or 1 trophies that I probably wont touch ever again :(