The issue though is that you're supposed to be just focusing on one expansion to level up to 'complete that story' but you've not going to do that if as soon as you've finished the levelling zones, you just skip off to Shadowlands anyway and leave the 'Big Bad' of the story you've been following behind.
Daily quests can be tweaked to make them into leveling quests and end game zones have a similar number of quests already in them. In Legion - Val'sharah has just under 400 quests in it, whereas Suramar has just under 500 quests for example. Even in BfA, unlocking Nazjatar and the Visions of N'Zoth questline could and should be part of the levelling experience.
Ideally, if they were doing this 'properly' Blizz could also give an option of a single player scenerio that would be an alternative to a full raid with a reduced number of bosses in there (2 or 3 main ones per the old raid?) as well as leave the actual raids as level 50 content.