It's not about having the balls. It's about having the actual means to do it. Biden/Schumer/Pelosi don't have the means, because they don't have enough senators on board with gutting the filibuster, especially for the purpose of packing the court. More than enough D senators have said they want nothing to do with it and won't weaken, let alone destroy the filibuster.
With any luck, they'll have even less of a chance at it after the 2022 mid-terms. The Dems that are saying they won't stoop to that tactic are doing so in hopes that they can still retain control of both houses of congress by not plainly going over the cliff into no-checks-and-balances territory, which would get them slaughtered in 2022, and they know it. The not-insanely-leftist D legislators know that not grabbing pure simple majority power is how they might actually hold on to the power they have, rather than burn it in a bonfire next year.
Even with the filibuster alive, the skin-of-the-teeth D majority in the legislature still allows them to control the legislative agenda (the Rs can filibuster things the Ds introduce, but the Rs can't force the Ds to take up bills the Ds don't want), and that's better for them than getting creamed in 2022.
Harry Reid already screwed the Demoncrats over while removing the filibuster for judicial appointments. Trump filled the federal judiciary with conservatives.