It was tonally jarring. Hey there's a giant army of undead marching south, they've destroyed the wall and zombified a dragon. Let's go for a little dragon ride for funsies and make Jon look like a bumbler instead of a heroic king of the seven kingdoms, then make out while a goofy dragon looks at us.
It would've been far better to have Jon be a relative natural to dragon riding and surveying his army and countryside from above while the people looked up at him in awe, followed by a scene with Dany along the lines of "I don't know what's going to happen tomorrow but I'm glad we could have this one moment for ourselves today."