3 main issues, in my uneducated mind.
1. Everyone is fighting to add velo and spin. There is only so hard the human body is capable of throwing and we’re asking guys to push that limit.
2. Youth levels and HS levels are getting too professionalized. Heavy emphasis on performance vs development has kids playing 1 sport, throwing all year, and throwing pitches they shouldn’t be throwing at a young age while their body is still developing. Has been an issue for a few decades now.
3. A change in operating procedure when dealing with certain injuries. 5-10 years ago this is an injury guys pitched through if it didn’t cause dips in performance. Many guys in the past have pitched a decade plus with UCL injuries causing soreness, but their stuff was still there so they just managed the pain. You can look at a scan of a perfectly “healthy” pitcher who has never had an elbow injury in their life and their elbow will look disgusting compared to your average Joe Schmo. Throwing overhand is not a natural movement, there is a ton of risk involved every time you do it.