BFA is far and away my favorite expansion to level in haha
edit: oh i actually read the OP lol, this is more about losing the borrowed power. I guess that feels bad but even before borrowed power systems, leveling in a new expansion usually was always that way ie: each level is harder and harder the closer you get to cap. Whether you're losing your azerite traits or just losing whatever tier bonus you got at the end of the previous expansion. They could "solve" this by having really powerful questing gear but, well, yeah.