Good game devs actually put thought into how to add visual cues for the player instead of using yellow paint.

Getting the player to look up without yellow paint and arrows

Teaching the player "flinging" without endless handholding

People will say there's no good alternative to yellow paint and then Valve will no doubt come along with another single player game at some point and prove that wrong

Nah, just draw a big yellow arrow. All devs do this. Don,t think, just lower the bar.

This is a puzzle game. The whole point of the game is to puzzle things out. Far cry or horizon zero dawn etc that use yellow/white paint are not puzzle games

i mean it’s literally the same thing, just a slightly more subtle version of it

One of my favorites is Doom 2016. They used green lights but they didn't feel out of place. Just perfectly blended into the world.

Portal has such basic environments. Hardly a fair comparison. A open world game with so much more visual diversity is a lot different.

Didn't these devs test similar methods and found that yellow paint worked the best

They never put yellow paint in their games so I doubt it.