The current randomness supports human life. I'm not so sure that whatever replaces it will too.

You mean the way mold is happily taking the place of entire coral reefs? Biodiversity is not just an ethical concern; biodiversity is useful to humankind.

If your randomness consists of oceans of jellyfish and insects as the most complex land animals, sure. If you want to actually get to witness the full extent of birds, mammals, and large reptiles, no amount of evolution will supplant those for several millions of years.