Started mtn biking at 53. Almost immediately went to clipless and right after that, hit the ground. In fact multiple times. First time out on the trails I fell maybe 4-5 times because I "couldn't" get unclipped. Not that I was somehow locked in, just hadn't learned to unclip without thinking. After that I don't remember falling. I use Time pedals with mtn shoes. Never fallen on the road bike because of clipless. It just becomes second nature, you don't even think about it.
Cannot agree with, nor understand the mindset you're somehow more vulnerable on a mtn bike, or somehow going to be worse injured. Everyone I rode with used clipless. You mtn bike single track long enough and you're going to fall. Clipless pedals won't cause it any more than platforms will prevent it. Nor will somehow your injuries become magically worse because you're wearing clipless. If anything, IMO it give you better control and more power when you need to really power over rough and gnarly trail, especially when climbing. When descending really rough sections, I felt it kept me "connected" to the bike giving me better control.