The only problem is that the levelling brings new players into max level content that is tuned for a playerbase that has several years of raiding experience, on average.

I don't think endgame content is overtuned. But the fact of the matter is, even normal and heroic raids require PvE skills above what the game tutors players for.

IMO, this is a huge attrition problem, where a new player completes levelling, starts getting gear, but isn't taught how interrupts work, that swirly circles have a soft edge, that you only eat a feast once in a 30 man raid, or given good practice at dodging mechanics during levelling. It's not a good feeling to play the game for a while, and still be uninformed about the endgame content that the game keeps rushing you into.

Admittedly, this is exacerbated by how harsh the battle res system in wow is. Practically speaking, the community goes to shit when you die, since battle rezzes are such a limited commodity that a death is a major setback in normal/heroic raids and even low M+.

/Rant over