That wasn't the point about the talent of people working on the game.
Red Engine is proprietary. If you hire someone from outside of the company they have to learn it from scratch.
Well, not exactly. They only have to learn the specifics of it from scratch. Most game development is done in C++ and art programs (many of those are similar). So most developers already know the largest and most important parts, even if the engine is different. It's not such a huge task as you think for them to learn it.
Besides, not all of them have to learn it or everything about it. Many developers have specific tasks, and some might not even have to touch the engine much at all, or only learn a very few things to do their specific tasks (example, creating textures).
Easier is often worse, and easier doesn't make the biggest talents.
Like I said, I'm also a fan of common engines, because they are extremely helpful to smaller studios, and as you say also, they are a great learning tool for people and even studios on their way to becoming a "big studio". Take Housemarque for example, an up and coming studio, or "smaller studio". They didn't have the resources or manpower to make/have their own engine. Unreal Engine was great for them in the process of going from a small studio to becoming a bigger one, possibly even a big one at some point soon.
Rocksteady is another developer I can mention. It's actually a talented studio, but I think if they want to advance/grow in the future to become one of the big studios of the world, they will have to make their own engine, that's what will make a big difference.
Now, CDPR going for UE, in my opinion, is a sure bad choice. I do hope I'm wrong, and I'd love for Witcher 4 to be great, but I'm certain it will not be, due to them using UE. And even worse if their staff/talent situation is so bad they have no other choice but to use UE.
