It is easy enough to conclude that these controversies just express a fundamental disagreement over capitalism: leftists oppose it as the root of oppression, whereas liberals see it as "problematic" at worst, and certainly not the center of any progressive agenda. There's something to that, but I want to complicate that picture a little by advancing a slightly different argument: liberals do not want to prioritize at all.
To expose that point, consider another issue: climate change. At the very least, climate change threatens to displace something like 2 billion people in the next 50 years due to coastal flooding alone; this says nothing of even greater threats like global famine and war. The worst case-scenarios are absolutely apocalyptic. And crucially, all of this is not only possible, and not merely probable - it's also imminent. If we are going to lower carbon levels before we start reaching climate tipping points, we have to begin immediately.
Given the scale and proximity of the danger, it seems to me to follow trivially that stopping global warming warrants literally any sacrifice we could possibly make. Nothing that we value is likely to survive the civilizational collapse that will accompany global warming; even if humans happen to make it, they will be cast into ruin, poverty and utter degradation, along with their lofty spiritual and intellectual achievements. If we get through climate change, we can live to fight another day the microaggressions in the latest Avengers movie or whatever; if we don't, both battles are lost.
Which is all to say that I can't think of any issues we should prioritize over climate change. And not only that, but we should be thinking about climate change the way #TCOTs think about Benghazi: everything we talk about that is not climate change is a distraction from climate change. If stopping climate change means accepting a totalitarian global autocracy that exercises absolute control over the world economy and carbon outputs with zero tolerance for democratic resistance, that is what we should endorse. If stopping climate change means that the US government leads a state-sponsored extrajudicial campaign of terrorism and assassinations against the global energy sector, that is what we should endorse. If stopping climate change means that we go back in time to when the Olsen twins were at their most innocent and adorable and drop them into a volcano as human sacrifices to appease the God Of Climate Change, that's what we should endorse.
I can't think of a moral argument against any of this, at least not one that is not entirely deontological. But are there any liberals in the universe who are prepared to think about politics this way? Would any of them be willing to vote against Hillary Clinton, Bernie Sanders, or even FDR if their right-wing opponent promised, credibly, to stop global warming? If so, it would be entirely out of character.
I fully expect any leftists who objects to this point to provide some explanation on how my priorities are out of order, or how my analysis is somehow flawed. Liberals, however, would almost certainly just make noises about "false choices" and "myopic obsessions" and so on, just as they do with leftists who prioritize economic issues. This is a problem with the way they think about capitalism, but it's also a problem with a way they think about the role of priorities in politics.