In terms of health, the biggest focus should be on reducing calorie intake and increasing saturation levels. It is listed as the #1 priority of the World Health Organization, and there is an argument to be made that its even mentioned three times in their top 5 recommendations.

Eat less. Eat less fat. Eat less sugars. The remaining recommendations are to eat enough vitamins/fibers, and to eat less salt.

From an environmental standpoint we should focus on bio diversity and sustainability which sadly very few of current food cultures fulfill. Increased use of shell fish and seaweed. Increase use of bio diverse farming. Reduced use of artificial fertilizers and chemical pesticides. Reduced use of fresh water. Increased hunting of invasive species. Increased use of grazing animals in nature reserves and area needing clearing (power lines and so on). Increased use of small scale farming and food waste management. Meat definitively has a role here but not in the mono-culture way that current industry meat production do it.