Maybe but in the early 1800s there was a guy similarly saying “The idea that people would voluntarily stop enslaving people and switch to paying wages is just wishful thinking” and yet we seemed to have changed that one.
I hate to bring the cynical take, but it has often been argued that slavery ended to a great extent due to economic factors (slavery simply not being so profitable anymore due to the rise of industrial capitalism, need of more skilled labor, decline of the profitability of plantations, cost of maintaining the system and stopping revolts, etc.).
Not saying that it was 100% economic and moral/ethical awakening didn't play an important role, but the economic changes definitely helped. And this kind of favorable factors aren't apparent in the case of convincing everyone to go vegetarian.
