This really isn't complicated. It is not unreasonable for people to assume that people will have a very basic understanding of the general aspects of the fight. Blizzard put the dungeon journal in game for that exact purpose. You don't even need to do any real research in advance since the dungeon journal is nice enough to give you 3 or 4 key points for your role (tank/healer/dps). It takes all of 10 seconds to open the journal and read those key points and you don't even need to leave game. So it is 100% perfectly reasonable to expect people to do that basic minimum amount of preparation. It's no different then "make sure you know the spells in your spell book and the basics about how to play your class." For everyone making silly comparisons to reading strategy guides, the better comparison is to instruction booklets. When I bought the original zelda it came with an instruction booklet, I read it, and then I was better prepared to play the game.
If you want to go into a dungeon completely blind without knowing what to do at all, that is completely fine but its not reasonable to expect other people to carry you while you do that. Make your own group and specify in the description that you are looking for people that want a casual run where they learn from trial and error. Based on the amount of people in this thread saying that's how the game should be played, it should fill fast.
On the other hand, it is completely unreasonable to expect people to know every mechanic so well that there won't be a single death or wipe on day 1. That's a ridiculous position to take and any raid leader that makes such a requirement on day 1 is just looking for a carry. This game wouldn't be remotely challenging or fun if it was possible to play without even the possibility of failure. There will be wipes on week 1. Period.
So its really just a matter of what "know the fights" means. Lots of people here are interpreting that phrase in what manner seems most offensive to them and then they are getting mad at that interpretation.