That is interesting… I stopped playing the game in WOD, long before I achieved Pathfinder. I came back about 2 months before BFA released and just started with Legion (rather than go back to get pathfinder in WOD). Through the course of normal gameplay (some dungeons, all the quests I could find) on one character, I got the pathfinder achievement. It took a few more days of grinding rep in Legionfall, but for the most part, just doing every possible story quest in the game for all the new zones, unlocked pathfinder. I took this to heart and revisited the character that had the most completed quest list in WOD, and realized it would only take a few days of grinding in Taanan…
It isnt that bad for players who do all the quests. I completed Pathfinder part 1 in BfA the same way… i picked ONE character (left my alts alone) for about 5 months (i know, I am slow) and completed pathfinder part 1 without doing anything other than questing and dungeons.
I think for players that refuse to do quests, or do a minimal amount of quests, Pathfinder will always be an issue…
I think each different type of playstyle (questers, pvpers, dungeoneers, raiders, etc) should have their own unique path to the flying achievement.