No, not completely pointless. Asking someone who has left Civ5 for Civ6 will get you answers from someone who has played both games, and decided in favour of the former, and can get you insight that someone who has only either played Civ5 or Civ6 can't provide. I believe the implicit question OP is posing is: 'What aspects/features of Civilization V made you come back to it that were lacking or not as good in Civilization VI, a game that is supposed to be better and more polished than its predecessor?'. The answers can be informative and interesting; they can reveal what sort of a game Civ5 is compared to Civ6, which is helpful for someone who has only played one of the two, and wants to know whether he will enjoy the other. They can also show how some new game designs and mechanics aren't necessarily good just because they were introduced later.
Though I agree that if OP wants a fuller view of the picture, he will have to ask in the Civ6 forum why some (or more accurately, most) people find that game better than Civ5.