I occasionally encounter this behaviour in Ex and sometimes even Savage but DF is by far the worst. Ignoring any instructions and help is a huge problem there.
It's completely fine to not get a mechanic immediately after seeing it or to not spot it first try.
If someone hasn't played for some time or is prone to taking really long breaks between doing a few quests, they'll most likely have forgotten about some things or don't recognize the tells immediately. That's okay, normal content is fairly forgiving and that includes the likes of Titania. Plus a wipe isn't the end of the world and if someone died to it and noticed "whups, I probably shouldn't stand there next time" they will watch out for it next time.
It's also completely fine if someone goes in blind because guides are definitely not required in DF and I have never, in all my years of playing FFXIV, met anyone barging into a duty and proclaiming that everyone better watched a guide or vote kick or get salty when someone died to a mechanic because they didn't know what was coming. On the contrary, if someone says "first time, didn't watch a guide" the reactions were always "no worries, blind is more fun anyway" - including from all those filthy elitist hardcore raiders.
So much for the hardcore mentality.
But if someone keeps dying to something, for the love of god, just read the party chat.
If people keep dying to Hydaelyn's weapons and someone writes "red = IN, green = OUT, blue = INTERCARDINAL" there is no reason to ignore it while dying to it another 10 times.
If someone confidently runs to a certain spot and jumps there, chances are that this is the safe spot.
If everyone is standing in one spot and a healer rescues someone into the stack, chances are they should stack.
But I've encountered a lot of "I do what I want lol" attitude. People run out of the safe zone they've just been rescued into and die. People ignore the short instructions in party chat. People ignore the marked person jumping like a bouncy ball in the safe zone. People completely ignore the movement of the majority and run around randomly. Not just new players, some older players as well. The older players are usually guilty of shooting down any instructions with "lol it's just normal".
I've seen a lot of vote abandons on all EW trials as well.
After the experienced players gave brief instructions, after they've marked one and told everyone who is unsure to just follow this person.
It wasn't too long ago that I spent almost an hour on Hydaelyn because even on healer with two capable friends on dps it was a huge mess and impossible to salvage to drag everyone to the finishing line.
Another boss I've frequently seen chaos to the point of vote abandons is the Bird. After writing "pull the adds apart before killing them, try to move in a stack for Searing Breeze, bird has double autos later so please put on tank stance and voke if you lost aggro".
Since it's not part of MSQ you generally encounter fewer people running around absolutely clueless about everything but Bird is still good for some "What the hell is even happening?" moments.