Most people won't even go vegan, that's like the bare minimum anyone could do that would actually have an impact, and most people won't do it.
Your optimism is not going to rewrite physics or change human nature. Go do whatever you think you need to do to make things better though, by all means, just don't lie to people about the unfixable apocalypse we're heading into or get shitty with them if they're rightfully adopting a bleak outlook.