Interesting analysis. However, I’m not sure democratic accountability is the main motivator here. I suspect that President Moon was more motivated by his service to his country than by a possible loss in the next election.
The problem is that western democracy (which South Korea seems to have adopted) does not consistently find the better people for governance. If South Korea elected a Park-like figure (lots of patronage) in the past, it can happen again.
The fact that President Moon was in charge at the time of Covid-19 is fortunate for South Korea. But we should not expect him to be there for long. Politics takes a toll on people, even if they are good politicians.
If the goal is to elect better politicians on a more consistent basis, may I recommend looking at alternative system of democratic governance.