It's not dangerous. You've been horribly misled.
I too was worried that it would block testosterone, and actually cause fertility problems. Then I asked by dermatologist about it. It doesn't work that way. It doesn't block testosterone. It basically modifies the testosterone to stop the harmful part of it.
You can believe the nonsense if you wish. I'll stick with a dermatologist with many years experience over the random health site dot coms.
A large amount of people on here know more about actual hairloss treatments and the side effects of hairloss drugs than dermatologists. So by you telling us you'd rather stick with the limited knowledge a dermatologist has on hairloss and the hairloss treatments actually makes your argument look even weaker than it already was.