I think you still have to be careful about folks selling training courses (or consulting services) to make sure that they aren't also glorifying complexity, even if they aren't trying to sell a product (or library or framework).

"You're wrong about the way you do unit test! Everything everyone is telling you is wrong! Fortunately, you can get my course that will clarify everything I just confused you about!!"

While I love testing-library, and have contributed to the sister libraries, one thing that always irked me is there was no empirical proof on why it was just better outside of handy wavy "because I said so."

Well, the more complex he makes things the more courses and consulting he’ll sell. It’s just marketing and his business model.