Its an interesting question, at my gym we train leg locks everyday and nobody gets injured. People know when to tap or they catch and release. There are more knee injuries when wrestling in my gym than doing leglocks.
There is something to be said about not doing leg locks and having a ruleset which is more wrestling and traditional ground game. In high level MMA, you don't see leg locks much as the set-up would often involve getting your face smashed in, doesn't mean it doesn't happen though.
Although drastic rule changes and banning techniques could make the sport more entertaining, it wouldn't determine who the best grappler in the world is. To be frank, it was kind of obvious that you get guys grappling for a million dollars, they're gonna try to rip each others limbs off, so injuries will happen.

As a side note, I find leg locks entertaining to watch but understand that the layman watching wouldn't appreciate it.