That's like saying he blocked stopping illegals from crossing the border. A pointless statement. There's no bill that McConnell, the minority senate leader, is blocking.

The DEA is run by federal govt, they work for the president. He has to tell them to reschedule weed. Biden promised to while campaigning in 2020, just like Obama did. Many dems have tried to pressure him to keep that promise. As for why he won't? Probably many reasons. Money, control, big pharma, elite's worry it makes people lazy and/or smarter. Right now laws against it aren't enforced (again cuz president controls what laws are enforced like immigration). But they might want the ability to enforce it again in the future. Every now and then you see fake news stories saying things like weed causes heart problems or other issues.