I've been skateboarding vert ramps most of my life (our ramp is pictured at the top of my site https://vertramp.org/). To avoid getting seriously hurt, (1) religiously wear pads (even wrists guards) and a helmet if you skate bowls or ramps, and (2) don't push yourself too hard beyond your current level. Pushing hard can result in learning more quickly, but it's also a good way to end up hurt, which has serious consequences at our age (I'm 44). I skate all the time with other vert skaters around my age; there's a ton of us (since vert was huge in the 1980s), and it is a very welcoming community. It seems like each year I do deal with one nontrivial injury - for 2017 it was that my knees just started to ache a LOT from my knee pads getting yanked when knee sliding on birch, which was the surface of our ramp before we put skatelite on it. In any case, you have to watch out both for traumatic injuries (where pads help) and more subtle injuries from longterm stress to your body. Skateboarding in your 40s is definitely very doable, especially if you optimize for having fun and getting exercise more than trying to be Bucky Lasek, who is older than both of us and a top pro.

Skateboarding is dangerous, but at least on a ramp or bowl, there aren't cars that can kill you in an instant, and (unlike surfing or snowboarding) where you are riding is mostly predictable and under control.