Broadly speaking, you probably agree with the large majority of the views commonly attributed to whichever group you identify with - what are the exceptions? Something that if you mention without a caveat immediately makes people jump to conclusions or even attack you?
As a trans person yes, absolutely the anguish we feel for not being comfortable in our bodies is 100% mental illness. And people get upset because we see mental illness as a bad thing, a personal failure, instead of a condition to be treated.
Doctors have decided that transitioning, while it doesn’t fix the problem of people not being born as their preferred gender, is much healthier treatment for the individual and society so that we can try to live happier lives where we get to feel as comfortable as cis people naturally feel.