> what are the practical steps one takes to "repair" or "renew" their gut?

Look up nutritionfacts.org and read/view it with a generous pinch of salt. A few years ago it took me half a year to switch to a mostly WFPB diet advertised there and I had no issues whatsoever. My gut is now more resilient, I remember having problems with bloating and/or diarrhea if I ate just a bit more fiber some days.

> why aren't we focusing on making healthier decisions for our diet, exercise, and mental well being?

The answers are there, but cognitive dissonance prevents us from recognizing or accepting them.