Here's a couple of facts to get out of the way. You'll have to accept them both (feel free to research). You can peddle ideologically driven arguments based on cherry picked anecdotal bullshit if you wish but you'll be wrong-
1) Eating meat at the levels we eat in the West is environmentally bad
2) Eating meat is not biologically necessary for humans
3) The more meat is mass produced, the worse it is if for animal welfare
So we need to eat LESS meat. Here's a thought- vegetarians define themselves to a degree by their diet. I know most actually don't especially want to make a fuss out of it, and it's often meat-eaters that bring it up and come out with unrequested bollocks like "oh, I couldn't live without meat" as if they had been asked to, but nevertheless these people are and consider themselves 'vegetarians'.
There are various reasons why being vegetarian is a 'thing', as opposed to being someone who doesn't eat say, raisins not being a thing. Maybe the very concept of people identifying themselves by whether they do or do not eat meat is getting in the way of the world just eating less meat.
Maybe if we weren't 'not vegetarians', if we were just people who eat food we might not feel the necessity to eat meat with every main meal. Meat-free things on menus wouldn't be the 'vegetarian' option. If people came to see meat as just an ingredient, would we eat less of it.
If vegetarians changed their sense of identity, and meat eaters took a slightly less reactionary position would less animals die? Or am I being simplistic?