I love flying, but really am glad Blizz makes the initial trips through a new xpac ground only. You do experience the game differently. That said I'm so glad all the alts get to fly!

The rep for flying isn't that horrible in BfA if you do the Emissary quests, follow the stories/do quests and use a contract for whichever you're lowest on (use to be Tortollan > Rustbolt).

Also don't forget Darkmoon Faire 10% xp/rep buff (Whee! or Top Hat too).

I still do quite a bit in Legion and WoD - transmog, finishing quests/crafting that didn't get completed, etc., and as I'm a mount/pet collector - class hall table quests to get paragon loot drops! I actually went back a month or so ago and did the class mount quest on all 13 classes. Besides it breaks up Bfa which was great the first few times, but getting a bit of a bore on the umpteenth time!