Ppl who aim for endgame only, are going to be disappointed with the amount of time and effort they need to get to that point after playing modern wow. I bet lots of them will drop off after it takes them days of gametime just to get to level 20-30...
Especially for those that started late, as in after Cata, it will be a huge pain, and I highly doubt they will have the patience and commitment that's required.
I don't have the time I had back then either, max 1-2 hours every two days or so now, but after playing the beta I still wanna do it, cos I love the journey, not just the destination.
The leveling is so different, and so much more deep in classic then it is in bfa.
In bfa I did use my lvl up tokens cos I couldn't be bothered to level through the same boring story again and again, as everything is so oversimplified that it's just pure boredom. With every class and race being equally balanced, with soloable elites, with no wrong choices in basically meaningless talents, and with any armor and weapon drop being equally good and thus meaningless, the leveling itself became meaningless. The only challenge is at the top content now, if you do mythic stuff, everything else is just a Cookie clicker with some reading involved if you care about the bland story.
In classic, every level matters. Every talent point matters, and you can mess up your talents the way you want to. Yes, I did mess it up big time first time around. By the time I was lvl 50, I had almost no points in retribution, and was doing sword and board with my dwarf paladin! Almost the most useless paladin ever, but I loved every minute of it! I could play whatever I wanted in 5man dungeons, cos I had points in everything! Not very well ofc, but it worked, no one complained when I healed them while dpsing and then tanked the adds off the mage...
Classic had this kind of freedom where you could make your character truly yours, something that modern wow sorely lacks with its "optimized" talents/armor/leveling.