Just seems ridiculous that the message is “everyone should give up their creature comforts and live as simply and tediously as possible so that billionaires don’t have to change”.

I never said that. On the contrary: All of it will have to change if life on this planet is supposed to remain livable, and it’s gonna involve quite a bit more than giving up red meat. I also think that having broad public support for that change, built on many individuals who choose to implement it, will make it easier to impose the same demands (e.g., through policy) on corporations and the wealthy. Given that billionaires are not exactly known for being selfless, waiting for them to do the right thing seems like a losing strategy to me.