I've seen and have had my share of injuries working takedowns. I'm old now and have no ACL in one of my knees. I don't practice them. Not worth the risk. Pulling guard works on the street right? :)
IMO the problem is not that practicing takedowns is dangerous, it is that most bjj guys don't practice breakfalls to ensure that they are not dangerous.
Suggestion: do breakfalls and harden up!
Interesting aside: when two guys start on the knees, the guy who gets the "takedown" is almost always the guy who would have got it if they had started standing.
LOL @ Pray Safe!!
Practicing breakfalls is helpful. If the guy doesn't know how to takedown safely though the best breakfall in the world won't keep you from being injured. I've seen it firsthand many times.
If you want to learn takedowns you have to practice them. Not much more to say than that. Do it in a safe way and practice against resistance.
If you don't care to learn takedowns then grapple from the knees. Nothing wrong with that.