I guess this guy’s never heard of humans being omnivores or that you can get protien from certain plants.
I mean, it’s not like we’re in an open system powered by the sun and the only way any of us actually get energy is because plants can synthesize solar energy and then mammals and other types of animals then eat those plants taking the energy they have converted, and now these animals convert energy from the plant into energy for themselves.
But yes, somehow, plants will cease to exist and functionally not be edible. /s