It really depends on the context. I don't think you should study every single leveling dungeon or story fight beforehand, as those are the kind of content you can beat without preparing for them. However, if you're joining endgame content that has a lot of mechanics to learn, if you aren't prepared it's possible the whole event time is spent on 7 other people teaching you the mechanics instead of making progress and achieving their goal. That's why I think it's courteous to do what you can to prepare for the content so that you're doing what you can to help the group progress.

However the best advice for these situations is to play with others who share the same attitude towards the encounter. Don't join PF groups or FC events that ask you to come prepared, maybe make your own groups for people who want to dive in blind and learn the mechanics by experiencing them. DF of course shouldn't come with any playstyle requirements.