It really is sad that people like you got flight removed from the rules set because they could not figure this out.
It is also too bad that you cannot figure out that when your party flys over the chasm, then deliberately walks into a cave to whack a dragon, one of these situations is desired, and the other isnt. I will give you a hint:They probably want to kill things.
They fly across the chasm because that's the most expedient way to get across. If they can't fly, they do it some other way.
They walk into the cave to whack the dragon because that's the most expedient way of killing it. If I gave them a wand of instant dragon slaying, they'd use that instead.
When presented with a problem, players look for the best available solution and use it. That's human nature. I don't give them cheap flight spells for the same reason I don't give them wands of instant dragon slaying: Because if they have ways to instantly bypass all obstacles, there's no game.