Yes, because everyone on earth with no exception is aware of all the knowledge you can find in the internet.
You did never work in after-sale services right ? How can you expect someone answering "internet explorer" to the question "what computer do you have ?" to know about the existence of rotations guides about the game they are playing ? Especially if the game did never told them that a thing called "rotation" exists ?
For a lot of people internet is just for facebook, mails, and buying things on Amazon. They don't even know there is patch notes and an official forum, and even less that there is some lengthy tutorials on the mmo they launch to relax after work.
And even if they were reading them, avoiding some problems like the tutorials being outdated (not so long ago i did see someone worrying about how to get the old cross-class skills removed in 4.0) or being in a foreign language they don't understand, that doesn't mean they will succeed to play properly. They can have physical disabilities that prevents them to do so, like in this QTE event who was only asking to smash some randoms buttons during a mere ten seconds (
https://forum.square-enix.com/ffxiv/...ore-QTE-please.). Or simply not being able to remember for long what rotation to do because (it might get as a shock to you) not everybody has a good memory.
That being said, i have great news : tiered DF already exists ! It is called PF. Open a "high dps, tank not losing aggro and using cooldowns, no zero dps healer" party, which will fill near instantly judging at the number of people complaining of underperforming players, and you are done. If you, as an invested player that know so much about the game, can not even take 10 seconds to do that, how can you expect way less invested people to spend countless hours reading guides and hitting a training dummy ?