Kennedy had his faults, to be sure. Was in high school when he died. Eisenhower had an average popularity, based on Gallup of 55% during his eight years. With the exception of Kennedy, no other president since, has managed over 50% at the end of their term. Kennedy's popularity was 70%.
Yes he escalated in Vietnam, it is also true that before his death he had begun to deescalte. Where he would have wound up is any one's guess.
No he wasn't healthy, but he was active, quick witted, charming, and thoughtful. Aspects any President would be blessed to have,most don't.
As for the moon project, having a goal and getting Americans behind something is usually political gold, win or lose, at least at the start. His succeeded.
Kennedy was a politician, one should not gripe to much about the man practicing his trade.
America was also very differnent then. Presidents were given some space to be themselves without everything having to be on the 6 o'clock news.