The current senator minority leader is Chuck Schumer. He's incapable of being an effective opposition leader. The dude is addicted to the status quo, terrified of rocking the boat, completely disconnected with the American people, and overall stuck in the mindset of a 20th century politician.
There is a lot of frustration with him among democratic voters, but he's maintained his power among the donors and other senators.
A huge part of his argument is that there's nobody else that can replace him. At the moment, he's not wrong. His rivals in the Senate are either cut from the same cloth as him, or are in their own way content with the status quo. I know people on Lemmy love Bernie, but the man was elected to the Senate the same year Pokemon Diamond and Pearl hit the shelves and is no closer to the revolution he promised.
While this filibuster doesn't accomplish anything itself, it's part of a larger effort Booker is making to raise his national profile and position himself so he can replace Schumer. In that context, it's an important and smart strategic move.
Ironically this filibuster was probably less physically and emotionally exhausting than trying to teach all of his Senate colleagues how to effectively use TikTok.