Threads like these have to be made since it is Sunday, I just wish they were more ignorant than this. OP plays for a few months, does 'raids' of varying difficult then says none of the mechanics of these various raids were ever in the game.
First off, I'll welcome you to the community. At its core, its an amazing game.
With that out of the way, the short way to address this is that every 'hard' fight has a 'normal' version. Now if you're considering 24-mans as hard....well, I feel bad for you. But every extreme/ultimate/savage, has a weaker version (ultimate is pretty much just a fight of bosses that were already fought on extreme/savage, just on crack).
Inside of all of these encounters have been mechanics you've at least experienced once in some form or fashion. They might LOOK different, but they honestly operate in the same fashion (like Zurvan's ground-pound thing that might knock you off the platform is honestly the same as Leviathan's boat-rocking thing). There will always be certain expectations (I'm sure someone can list/has listed/honestly didn't read enough to care); however, part of 'belonging' in higher end content is having the ability to adapt.
This isn't always the case since most fights are just patterns at the end of the day that look more complicated than they really are after you've done them enough, but if you've honestly experienced EVERY mechanical pattern on a lower difficulty as you did in the higher one, it would lose its appeal since the only difference would be damage. Now if you need a game that spoon feeds every single thing to you, there are other options, like WoW which has about 3+ modes for almost every instance content or one of those f2p games.