I'm fatalistic. You'll notice when I first mentioned Myco, I said it was a politically charged subject. For obvious reasons, a lot of people who sell fish don't like to talk about it. That is made easy because of the nature of the disease - it produces a ludicrous range of symptoms that other diseases also produce, and is hard to 100% diagnose without dissection and a microscope.
It scares the bejeebers out of people because in rare cases, it can jump the species barrier and we can get it. I did. But that's like getting hit by lightning - a known possibility but very uncommon. I saw a professor of dermatology at a major medical school, and he had only seen it in photos. I felt special!
It also afflicts swordtails, platys, mollies and other harder water fish - it is a marine disease originally that has adapted to some freshwater populations.
I try to buy all my fish either wild caught (not many of us have that opportunity) or from hobby breeders. A little digging, and you'll find rainbow fanciers in the UK.