FFXIV's high-end content is, without a single question, something that you'll want a regular group for. I basically quit because I couldn't convince my friends to keep playing. Partyfinder isn't usually toxic, but it's always draining because high end content doesn't really let you "carry" somebody and if a single person leaves then you'll most likely be starting fresh with another person who has never done the encounter before.

Yeah, in MMOs it's expected that you'll study up and not waste everyone else's time with your learning because you're largely playing with complete strangers that you'll never meet again and everyone just wants to get it over with. But in this game you're playing with max 3 other people, runs are quick, and nobody's likely to be in a huge rush either way. Also, unlike in a ffxiv EX trial, it's pretty difficult to fuck up enough that you end the run on your own. If you're messing up other people and getting them killed, most likely you're getting yourself killed before them, and your teammates can then keep going in a slightly easier fight since they don't have to play around your unpredictability. Then you can spend your respawn time studying how they do the mechanics, which might help you handle it better once you do respawn. Or they might finish up the fight without you depending on how far along it was.