Your portrayal of FDR is extremely unfair, and shows your biases clearly as day. The man was re-elected for his 3rd and 4th terms in 1940 and 1944, think of any extenuating circumstance that might have caused that?
Extremely unfair? After he did that, a Constitutional Amendment was passed to stop that from happening again. Presidents have an enormous advantage in reelection, and the country was concerned that we were at risk of a "president for life".
He was quite ill during his final term, which put him at a severe disadvantage in negotiating with Stalin. This was hidden from the public.
Because the American people don't really choose who's on the final ballot. For all we know FDR in 1944 was considered "just ok", but was better than his opponent.
Then that was the fault of a lack of a challenger within the Democratic nomination. And if they really wanted to, more delegates should have voted for Harry Byrd:
Given that Americans tend to reelect presidents during wartime, that makes the claim that FDR was somehow unpopularly "just ok" to be even more dubious.
He was quite ill during his final term, which put him at a severe disadvantage in negotiating with Stalin. This was hidden from the public.