For example if we do something relatively small like ending beef subsidies here in the US, then ground beef will double or triple in price, and people will naturally consume much less.

And you think people will be okay with that and just let it happen? A politician does that and not only are they not elected again, they might have protests and even riots on their hands. You can't post c/vegan without non vegans showing up and being disruptive. Which begs the question: why would politicians ever do it when they know this?

You can't have systemic change if people aren't willing to change their lives in the first place. People often say they want this or that, but don't actually stop to think what that requires. Survey's also show that most people want carbon taxes, but look what happens when the price of gas goes up. What do people think carbon taxes will do? Well, the answer is they don't really think about it; they just think "tax for company to help climate", and that's where it stops.

If you want systemic change, then you also need to acknowledge and raise awareness to the need to take accountability and change our own lifestyles, otherwise that systemic change will never work. Going around saying we could all "change our lifestyles and it wouldn't matter" and that "what we need is systemic change" in response to people talking about taking personal accountability, does, ironically, very little to bring about that needed systemic change; or at least that's my perspective.