It's not that simple. Problem with dance routine raid encounter design is that there is no natural skill accumulation and each raid encounter is its own contained game. A group of players who figure out the dance routine for one boss has to learn a new dance routine for another boss and if one group member leaves then the rest of the group needs to wait until the new guy learns all the relevant dance routines. This is why guild recruitment turned into job interviews. This pathology leads to another pathology called "Is it too late to start X?" which is open admission for someone realizing they might as well not join the game mid-patch because of impossibility of acquiring enough dance routine knowledge / time-gated gear to meaningfully participate. The problem is further exacerbated with the game being effectively redone each expansion with drastic overhauls of talents, gearing and skill rotations. Someone who left the game in WotLK and rejoined now would be no different from a geniuine new player who never played the game at all. None of the original game aspects transfer between each itteration and each WoW expansion might as well be a new game entirely. A long-term player doesn't really accumulate any relevant experience or meaningful prowess so they become completely demoralized. Why bother learning your class's skill rotation when you'll be forced to re-learn it next patch? You could slave away in front of a training dummy in Stormwind and spend 2¬3h training your muscule memory to maybe perform on acceptable level (and probably develop carpal tunnel overtime if you play more than 1 class) or you could spend all that time and effort into doing some overtime at work in order to purchase a subscription from AimSharp or whatever 30$/month rotation bot people use these days.

Alas, my post is based on Shadowlands which made me leave in disgust so perhaps a good chunk of what I'm writing may not be relevant to current WoW situation.