I agree with this, even if you increase the difficulty on a guardian it's still a gueardian, with the same strengths and weaknesses. It would be cool to see more enemy variety in shrines, but with them being tests by the sheikah it'd be kind of cruel to stick a moblin underground for centuries.
I don't really recall any specific shrines I liked or disliked, but there are some general types I prefer. The apparatus shrines, while annoying, are actually kind of fun to mess around with. Having an excuse to pull off my joycons and flip stuff into the air is cool, and it's really satisfying...