You are absolutely right.

With sustainable methods, we would have to severely cut down meat consumption or depopulate.

I wouldn't say I propose a solution, but there is a middle ground and quality is very important.

If you think about it, photosynthesis is about 4-6% effective while high end solar cells are about 20%. LEDs give you a yield of up to 60%. So we could look at a future, where farmland is not required.

Seems strange, but growing plants below a city could be even more sustainable then on farmland.

Making everyone go vegan definitely isn't.