the normal content is too easy

[vetch]

That is definitely part of the appeal of repeating content for many people, in many games! However, many dev teams will see a difference between "Look at how quickly I've got this down to run it after all my practice!" (e.g., speed-running, which you reference) and people trying to do things in the fastest way possible the first time through.

(Source: Used to work at a game company professionally.)

After all, even if you get the newbie message at the beginning of an ARR dungeon, I rarely ever see people interested/willing in going down those side pathways for the sake of the newbie.

You're ignoring half my argument. I specifically said side paths need to have rewards to encourage players to take them. A lore note can be important to a small subset of players, I do like reading them, but it's not a reward for 95% of us, not even the first time through. If you put quest objectives down them, or a chance at a cosmetic with no other source, or give extra daily rewards for clearing a mini-boss, more veterans will take an interest.

While I'm inclined to agree that it is not the majority of the community, demonstrably there is a subset of players who in fact would do precisely that; the fact that folks would not let first-timers watch the long story cutscenes in ARR dungeons is literally why the cutscenes in the Praetorium were made unskippable.

Four years ago. Yet, the extremely long cutscenes in Stone Vigil, Toto-Rak, Ifrit Normal, etc. were not made unskippable and yet I've gotten them in roulettes over and over for almost two years of playing and not seen people hassling the new players for watching them. Game moderation and community policing (informed by the moderation) have served for that, so let's not you and I pretend that there's no other way to handle jerks than to core out the game design.