Instead of trying to improve me or berate me, you need to sell me on your candidate.

That decision process was what the Biden campaign was trying to avoid.

Not every voter - not every "me" or "I" in your formulation - decides to cast their vote this way. Some voters, before they get to a comparison between the candidates, will reject a candidate out of hand as just being unsupportable. Disqualified. Unacceptable. That regardless of the merits or policies of the other candidate, they just are never going to vote for the candidate that has the undigestible defect.

IOW, the Biden strategy was to make it about Trump. Get enough voters to decide that Trump was simply not an acceptable candidate as a threshold matter, and then you don't need to sell them on Biden.

That was a winning strategy in 2020....though re-election campaigns are often naturally "referendum" campaigns, where voters' first assessment is how they feel about the incumbent before moving on to the challenger. They were going to run it again this year.

But now, that campaign strategy can't work any more. It only works if there's nothing truly disqualifying about your own candidate. If your opponent has a fatal flaw, then any voter that agrees with you that it's a fatal flaw doesn't need to be sold on your candidate. But if your candidate also has a fatal flaw, then - at best - you're asking the voter to balance which fatal flaw is worse. And for some voters, they might look at your candidate's fatal flaw and stop there.

The Biden strategy already wasn't working too well. He was in much worse shape than in 2020, despite Trump's fatal flaws. Partially that's because (again) voters have an inclination to view re-elections as a referendum on the incumbent, and partially that's because the flaws Trump exhibited as President were several years ago. So they weren't top of mind for many voters.

The plan for the debate was for Biden to refresh voters' memories on the Trump fatal flaws - which might have revitalized the Biden campaign. What happened was that Biden put his own fatal flaw in front of the viewers. The original Biden strategy now has virtually no chance of succeeding, because Biden won't or can't do what he needs to do to erase voter doubts about his mental acuity.