She does seem like an actual leftist I'll give you that. But rhetoric doesn't count for much, what has she actually done that's radical?

I can only judge from her Wikipedia page but under political positions it says "Her platform has included universal healthcare, stronger tenant protections, funding programs for children instead of funding war, abolishing US Immigration and Customs Enforcement (ICE), banning large super PACs from elections, and prohibiting members of Congress from trading stocks." And she opposes Israel. I'm sorry but that doesn't read as extreme to me. Maybe abolishing ICE.

What has AOC done that's "far left," or Mamdani? They can say what they want but none of these people actually threaten the status quo of American capitalism and imperialism, which (in my mind) anything worth calling "far left" must do to be valid. Bear in mind the standard on the other side is an attempted coup with a gallows on the Capitol lawn. BLM at least took over a police station and started a separatist autonomous zone. That's what "far left" looks like. Not "we need rent control."

Actual far left movements like BLM and Occupy get co-opted and undermined before they even have a chance of affecting change. If any of these people even so much as glance towards the White House they'll be crucified by the Democrats, because the biggest problem with leftism in the US is that the only even ostensibly "leftist" party with any real power hates the left almost as much as the right does.

I wish the DSA luck but I expect absolutely nothing of value from them. Wake me up when they're hanging billionaires from lampposts and then tell me about the "extremism" on both sides.