I mean, I'm all about protecting animals but the reality is that things become extinct. For whatever cause, natural or manmade, it's just how it works. Species kill off other species. Some probably before they even had a chance to propagate. Will it suck if Lions become extinct? Yes. But will it really have much bearing on anything in today's modern world? No. Besides, we're not too far from being able to recreate whatever we want anyway.
Extinction of certain plants and insects is much more problematic than losing the lions or polar bears.