Supply chains don't completely rewrite themselves overnight. Shutting down meat distribution doesn't help people eat. For the time frame of '2020', the meat industry is essential.
We have shortages in supermarkets and food rotting on farms at the same time. Rewriting a supply chain is hard, and your amazing line-drawing skills aren't going to fix that overnight.
And you didn't even address how much of that plant matter doesn't meet human quality standards. Even more to significantly rework.
But on this topic I'm better off talking to the wall of bricks next to me than the HN audience