My issue with this whole "watch a video before you get into a hard fight" mentality is that it does nothing to fix the issue that's at the core of this: people don't pay enough attention in a fight.

If you're paying attention to what is going on, it should only take one or two deaths to figure out what you should be doing to prevent the death (obviously some fights are more mechanics prone and you'll die to the next one and so on but still). If people are actively paying attention to what's going on they'll notice the queues, notice what more experienced people are doing (in the case of getting the instruction of "nails ASAP" and not knowing which nail to go for).

Mechanics based fights are entirely dependent on situational awareness, which a lot of people seem to lack.

Please note; my opinions are of course limited to the content in this game I have completed up to and the content in other games I have participated in.