I totally agree with this notion, everybody should do what they realistically can, and it will look different for everyone. Some can be vegan and it will work out great, others will struggle to give up meat. Some can bike/walk to work everyday, or avoid air travel, and some can't. Anyone doing well 80% of the time is probably doing just fine.

All that said, it is worth remembering that these industries are (mostly) funded by consumers, and while giant corporations are obviously the way bigger issue, consumers have more power than we often give ourselves credit for to restrict those companies. In a hypothetical world where everyone stops eating beef, it isn't like the beef industry continues to pollute. They will directly produce the amount of beef people will buy. Even if everyone has their steak now and then but doesn't make it an every night staple, that alone would already do a lot to limit the emissions of the beef industry. It's not a whole solution, but it is the one that is easiest and most obtainable, because convincing the government to stop subsidizing beef is not on the agenda of any major politicians at least in the states, even if I wish it were.