You gotta complete the quest (and dungeon) to even continue MSQ, the flight aether is just unlocked with it.

If you are worried about playing with others, be aware that in shadowbringers, you can run all mandatory dungeons with npcs as your party members. It's called the trust system.

Also I assume you are aware that it isn't just completing the MSQ that unlocks flight, you also gotta find all the other aether nodes and complete a few other (very trivial) quests.

They aren't gonna change how it works though, it's been this way since flight was introduced