I eat a lot of dairy and fruit and veggie during the day, along with a limited amount of bread, not white, unless I eat it just before cycling home so I can use the glycogen spike. Of course working means it's hard to always have the time and motivation to stick to that diet, but it's what I try to follow.
In the evenings I have recently started eating more vegan, with things like cusco, quinoa, kidney beans (have this amazing recipe for burgers using kidney beans) lentils. But then there are days where I eat meat.
I just think you need to find a mix that suits you and gives you enough variety. Personally I think only eating meat, or rather saying every dinner I want some form of meat would be boring after a while, but likewise cutting it out completely, would be too.
In terms of sustainability, sure meat has a bigger impact. And in the long run, humans definitely need to limit the amount of meat being eaten. But I do not think it is necessary to do so completely.