100% This ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Guests to WDW can't fathom closures. This is proven by countless threads here and elsewhere about how vacations are ruined and such because favorite rides/attractions aren't open. Well people, let this small example be something that stands out!
Yes, it's WDW. Yes, it'd be great if everything were always open. Sadly, things break. These transportation options are used and abused heavily on a daily basis, the rides go through far worse abuse. Things strain and break and need downtime.
This is one of the reasons I think they got rid of the 24 hour events. There literally was no downtime for maintenance to maintain the rides.
They'll patch Blue up and it'll be back running again, but people need to learn that if something has to go down for a major refurb, that it's for their safety to do so. Not because Disney is trying to be a PITA and ruin their vacation.