I’d ask if this is your experience or just what you believe? I eat instant mashed because I looked at a package one day and found it contained nothing but potatoes.
Take a look at the grocery store - there are at least two major brands that list one ingredient - potatoes.
I got my first microwave in 1988. It is not a dial one. I say “IS not” because I gave it to my friend over 10 years ago and she is still using it. And it works.