A problem i see with it, Shards/servers without flying would force blizzard to develop either different games, or without taking flying into account. Never again would we get zones like Stormpeaks or Icecrown, where the flying was an integral part of getting around the very vertical landscape.
Whenever I think of life without flying I think back to levelling in grizzly hills in wrath of the lich king and how many times I accidentally fell off a cliff to my doom and had to spend 10 minutes getting back to my corpse.
In the vanilla zones I think not flying is pretty enjoyable but in practically every other expansion flying just makes the game better imo due to how the terrain is designed.
I think the problem with it is that some non-flyers don’t want to do PvP and they’ll feel forced into it just to play the game how they want to, and on the other side of that, people who love world PvP are forced on the ground and not everyone will be okay with it.
I understand human nature just fine. It is you that does not understand that people are different. Not everyone will climb something because it’s there, unless it gives some kind of advantage or reward. The person who feels accomplished for jumping their way up something, good for them. The person who feels their time is better spent doing other things, also good for them. No judgements are needed or snide comments about what people feel is or isn’t an achievement/accomplishment.
The big irony here is with Shadowlands, it has done exactly what you claim it shouldn’t. It listened to the playerbase. I feel very listened to both by what has been released at BlizzCon and most of the information since. I am very much looking forward to getting to play the next expansion. Alpha so far has also been great so fun so far.