There is this screen on specialization selection window which lists 6 main spells. That's enough to maintain basic rotation for a new player. It won't make you a pro, but it's a decent start.
I think what you both say is not contradicting. Vanilla, TBC and so on was much more simple and didn't require much skill to play well. Over time complexity kept increasing and the skill's impact was more visible. Now people, who could play decently in the past, are not skilled enough to play at the top performance anymore. And it's a good thing.Vanilla - spammed 1 button
TBC - spammed 1 button
WotLK - the start of actually having something of a rotation
each next expantion - improving on rotation, making timings more important...
Yes, totally spamming 1 button requires as much skill as actually doing an optimized rotation while having to actually change your position quite often due to mechanics.
The bad thing is that elitists try to pug stuff and those do not have patience to deal with any performace lower than their own ^^