Tim says he will never go back to randomized skill checks. Save scummers ruined it for everyone.
Are we sure it's that, and not all those times people argued with him over randomness?
Going back through some of Tim's prior videos, I found one issue I disagree with him about: his preference for RPGs where you make one character as your avatar in the game world, with the idea being that it encourages replaying the game to have a different experience. I agree, in theory, but those games have to be "worth" playing through another time.
Not only are there all those other games to play, or other things you could be doing, but a lot of times the game itself can be a problem. If you've played a game before, it can be easier to get through stuff that challenged you the first time. On the other hand, you know all the things about it that bothered you, either because it's objectively bad design, or because it's personally aggravating.
One example for me is Tunic: it's not an RPG, but it's a game I really wanted to like. Except interact and roll are assigned to the same button, and those features can't be separated via remapping. You might think it killing me in one early boss fight was why I hate this, but it's not. It's rolling like an idiot
every time I try climbing a ladder, because I press the button before the context can switch. I'm not in danger of dying or losing progress, but whenever I think about the game, it's all I can think about because it's such a stupid, unnecessary problem for the game to have.
An example from an RPG is Pillars 2. One incredibly small thing that aggravates me about this game is that you can get a ring that's supposed to stop you getting drunk, but it's flat-out useless in a drinking competition you come across later. I've tried playing this game multiple times, and every time I come across the ring or the drinking competition, it bothers me again.