Yeah, I know. I converted both videos long time ago and didn't care much, the time track is completely out of space.
Well, you decided that it's shit just because in your mind it can't at all. So, why can't I imply (because I said nothing) that it's not as bad as this, while proving it.
Mostly for two reasons, cumulative or not: They don't have the bit of coding knowledge it need, or don't need them in their game.
Winterfire already partly answered you ; and he know what he talk about, he did games with both Ren'Py and Unity.
But the main reason is simple: Because there's people like you who pass their time claiming that Ren'Py is "bad at this", "can't do that", while being wrong.
This lead some devs to believe that they'll need to use Unity for their game, because they have such great ideas. While in the end doing a game that absolutely don't need it, because they are lost and don't know how to implement their ideas.
What limit Ren'Py games to mostly VN is more the dev than the engine, but the dev. RPG Maker is easy to use, but limited. Unity is unlimited, but harder to use. And Ren'Py stand in between, being easy to use with really lax limits.
The realization isn't really great, but the best example of the wrongness about Ren'Py's limits is probably
Lust Hunter. It's a Ren'Py game, yet it have a big dressing system, a RPG Maker-like map (with the assets directly coming from it), and an interesting combat system.
Doing it with Unity wouldn't be more difficult, because there's templates for most of the needed content. But neither would it be easier, because C# need more coding knowledge than Ren'Py ; something that most Ren'Py devs lack of, ~90% of them never had done coding before starting their game.
I'll even go further. I don't remember the name, because it never goes far, but when I registered, seven years ago, someone achieve to do a VR realtime 3D demo in pure Python. It was like the "fuck her how you want it" demo that also exist with Unity and Unreal, and that also never have been finished.
This mean that, as long as you've the knowledge regarding 3D algorithms, because you'll have to write them, Ren'Py could do real time 3D. Obviously, it would be more limited than Unity, Godot or Unreal, but it would be enough for a game like
The Twist by example.
What's missing isn't the capabilities, but a template for the devs who don't know how to code this. Because if you've the knowledge to do it yourself, you also know that using C/C++/C# for it would be easier.
Side note: If someone remember the name of the game or, better, have a link, I'm interested.