Our economic systems only work with infinite growth because otherwise what would be the point of lending money if it won't grow interest. It's essentially a giant pyramid scheme. And that requires new blood to provide labour and consumers. This is incredibly dumb on a finite planet with limited resources, but that's mainstream economics for you.
Also if the population shrinks too fast, then the pyramid becomes unstable with not enough younger people to take care of all the old people (while also maintaining the economy).
I don't think that anyone in this chain of replies has argued for flat out ending all animal meat production. Sure, plenty of vegans are motivated primarily by animal ethics and thus want to categorically ban growing animals for food, but here almost everyone seems to be talking about the sustainability aspect of modern mass animal agriculture, myself included. Although less ethical scruples is a welcome byproduct in my opinion.
I'll take lab grown meat seriously when it's been proven to be financially competetive and most importantly scalable. Technofixes have a bad track record of turning out to be mostly just investor bait. Kinda like all the bullshit high-flying transportation concepts as solutions to problems where just slightly better urban planning and prioritizing public transit, cycling etc. would work wonders.
Plant based food on the other hand has been most of what we have been eating for most of history. It wasn't that long ago when meat was still considered a relative delicacy, back when scarcity necessitated efficiency. That's the kind of efficient, sustainable, healthy and local (so logistically simple) food production system we should try to strive for in my opinion.