They aren't wrong, though. The Democratic Party isn't really leftist so much as centrist to center-right. I think the last real "leftist" administration we had was the Carter administration, and he's the most reviled President in American history (or at least in the top three with Trump and Nixon.) Americans just don't have the stomach for true leftism.
Biden has made some good attempts at rebuilding government infrastructure and restoring environmental policy and gets an E for effort at student loan debt, but he's still pro cop, pro military, supports business over labor, and buys into the myth of American exceptionalism too much to be considered "leftist."
Even AOC seems like more smoke than fire lately.