You have a point, but let me ask you: if a bag of rice had been the Republican Presidential incumbent in place of Donald J. Trump, do you think Biden would have received a record-setting number of votes?
Maybe I'm wrong about this, but it seems to me Trump's unpopularity was as much a factor in Biden winning as anything else that, and maybe that's because I live in a blue bubble, but even conservative outlets I followed were expecting the Republicans to be absolutely crushed this election and to go down in flames with the President, and they weren't. Not even close. Republicans didn't regain the House, but they saw net gains, and they retained a full 50% of the Senate. Harris's vote is only relevant if the Democrats can win in the Georgia runoff on January 6th, not just one, but both seats, otherwise she's just another President of the Senate without a vote. Considering that election is still an open question, it is a bit early to be calling Georgia a blue state. Elections are more than just the President after all, and Red and Blue States are only really Red and Blue after they've demonstrated a continuous unbroken Red or Blue streak for a few cycles.
So again, if the Republican Presidential incumbent was a bag of rice, would we have 1. seen record-breaking turnout in favor of both candidates and 2. a loss by the incumbent? I ask, and maybe this is just because I live in a blue bubble inside a blue bubble, because it seems to me much of the public turned out to register a vote of no confidence in the President more than they turned out to vote specifically for Biden. I wouldn't say most of Biden's votes were this, but enough to swing the election in a few key States? I think that's plausible.