They did SoM too soon, which is why they’re not doing TBC servers. They thought that there were enough people interested in staying in classic era, there wasn’t. So they thought to reignite interest in classic with SoM and all the changes it brought. In the end though all it brought back were a small size not even the size of a medium pop realm spread across 14 servers 7 of which have no players.
If they were to do SoM in say… 5 years or something, I still won’t play but I’m sure that it would’ve had more interest than it has now. It’s all about time.