I think that it was necessary as WoW got so big and there are now the base game + nine expansions worth of content to level through.
I do agree overall it kills the sense of progression, and classic era leveling is way more fun. But I don’t think that is sustainable in a game that lasts this long.
It was to a point you are changing zones every hour and you could barely finishing anything.
It also made dungeon queues a mess because each one had such a narrow level range. Now leveling dungeons are still awful, but it’s because they are tuned so bad.