The microwave has two big related issues (both mentioned in the article).

The first is that it is not easy to make a mental model of how it works. The second is that since it takes little too cook the food, it is unforgiving and you have to be very careful with both timings and amounts.

This makes it hard to learn how to properly use it just by trial and error. Also since now we have inductive stoves there is even less reason to use it.