There’s Finasteride which is used for this. It inhibits DHT specifically and not testosterone.
Testosterone blockers like Spironolactone would be problematic longterm because having low levels of both testosterone and estrogen comes with health risks like osteoporosis. And you can still get feminising effects like breast growth even if you don’t take estrogen. And it seems like most men would like to avoid that.
It does work though. Trans women on hormone replacement therapy usually don’t get male pattern baldness. I’ve had a bit before I started HRT and some of my hair has even grown back (that’s not guaranteed though).
In my case, probably, but I was like 14 by the time I read the last book so I don’t really blame my younger self because at that age I definitely wasn’t looking for any deeper meaning and just enjoyed the fantasy and escapism.