He's right about the painted ledges though. I have no idea why they're still a thing. May as well watch a five minute cut scene of the character climbing with some nice scenery in the background.
They exist because not any devs wants his level design being trivialized by free climbing everywhere.
In botw there is nothing stopping you from climbing that giant mountain with 10 stamina potion in your inventory and just pressing up in the controller instead of finding the optimal way.
And in the last 2 ac, you can basically assault every camp from every direction or not even thinking about skill in parkour movements because you can simply climb every fucking thing.
I know it's great in theory and work in some cases, but not all games require this or it's easy to implement.
Imagine aloy climbing a mountain and fucking all the dinobot from a safe place instead of fighting the right way, you can trivialize a lot fo things with free climb.
I recently re-played infamous 3 and in that game you can literally destroy all the enemy camps from high buildings without them being able to even hit you, yeah it is a power fantasy but say goodbye to any form of challenge with people exploiting this stuff.
Tsushima has some sort of ambiental puzzles that require platform movements and specific points where to use the grapple hook etc, with free climbing you can say adios to any form of puzzle.
The collectibles in spiderman were absolutely the worst because spidey can reach any fucking point so it just become trivial searching for them.
Sometimes good level design and puzzle need to restrict player movements to work correctly.
Jist look how many games have free climbing everywhere, just a couple.