Yes, allow people to ask a friend to de-level themselves or to create a fresh character so they can experience Eureka once again with someone. The number of people willing to do this even for friends is far and few between.
You see, I would have also been willing to give you some kudos here, but apparently reading really isn't your forte. The issue isn't with people wanting or treating MMORPGs as single-player games. The issue is related to the game having a lack of a system in place for those more adequately levelled to help those whom they are friends with of a lower level without restarting a fresh character.
Maybe stop trying to jump to really wild conclusions regarding the premise of a post and actually elect to read the post in the first place, and then actively try to examine why the lack of down-syncing yourself could be deemed an issue - and an issue that actually conflicts with your premise of 'maybe people should stop treating MMORPGs as a single-player game' - Maybe if the game would allow me without being overly inconvenient about it.
Let's examine this shall we, in case the implication has gone above your head.
In order for me to help or join a friend without them being inconvenienced I need to either:
1. Resort to exclusively just pop NMs in order for them to level, to which their reward will significantly diminish.
2. De-level myself to the lowest possible level so that I can farm monsters with them.
3. Create a brand new character and either skip through the entire story or purchase a job skip in addition to a story skip.