Legislation and enforcement only played a partial role in reducing the rate of driving while intoxicated. DWI was still normal and socially acceptable for decades after we started banning it. We changed our attitudes, we stigmatized the behaviour, we created new norms, we invented the concept of the "designated driver". Millions of people had to be the first person in their bar to say "just a club soda, I'm driving", the first to say "don't you think you've had enough?", the first to take the keys out of their friend's pocket and call them a taxi.
It's absurd to think that we can solve the problem of antibiotic resistance just by personally giving up meat, but it's equally absurd to think that our own choices are irrelevant. Collective problems are just individual problems at scale; the solutions are also the aggregate of lots of small individual actions. Eat less meat, buy better meat, lobby grocers and restaurant chains to sell antibiotic-free meat, write to your representatives, inform your friends and family about the issue - it all helps to move us in the right direction.