I think a good compromise would be when you enter a dungeon, cavern, non-friendly keep or tower etc you can’t long rest until you leave again. That would up the stakes dramatically and make those regions more about resource management. Short rests would become much more precious.
Perhaps you need to stay out in the open for a while until you’re strong and confident enough to take on that dungeon. Would definitely make the game more tactical, and remove the ridiculousness of teleporting in and out of the underdark at will before you even get a teleport spell.
