If you’re worried about cultural factors, you might find removing any significant percentage of the total population will likely run into even more implacable “cultural factors” than meat reduction would.
This is regardless of the method of population reduction, save perhaps “slow decline” which seems to be promising atm, but that obviously has the downside that it’ll take a few generations to really have an impact.
Fair, we certainly won’t see any perfect or even good solutions given human nature and the large population, but I do think we can achieve mediocre success if we really work hard