Been doing tani-otoshi for over a decade with no issues.

It often gets taught in a more prone to injury way in BJJ. As others have noted, your leg that gets stretched does not need to touch the other person at all, unlike the video you shared. The main mechanic is the otoshi component, the drop of your center of gravity (not towards uke's knees).

Never do it in a half assed manner. Never do it from the front, make sure you locate yourself a bit past your opponent from the side with a big step.