A full democracy would mean going to a time where every single vote accounted directly for every single action taken. Then again, this is most likely a figure of speech to further a claim or perspective. When he says full democracy I would assume he is hinting at moving away from the way the government had been run under the Trump administration, which can be alleged to have been corrupt due to the manner by which the majority of the Republican party seemed to follow Trump blindly, many times despite the requests of voters or constituents. This is furthered when looking at approval ratings, which were very low during Trump's presidency, hinting that the majority of the US felt as though they didn't like his administration, something which could be called "undemocratic" in certain contexts as it goes against the will of the people. Essentially, It wouldn't be ironic for Biden to say this unless you consider the way the US works, in which we elect others to make decisions for us.