If Daenerys had used one of the dragons to scout south toward Dorne maybe she could have spotted Euron's fleet. Additionally, it wouldn't have taken long to fly over to Casterly Rock just to see what's going on over there. Seems like she could be doing more than sitting on her stupid throne and coming up with new titles for herself.
They have to nerf the dragons. Otherwise they're the solution to pretty much every single problem in the world, the undead army gets roasted, Kings Landing falls in 20 seconds and Cersei becomes Dragon Snausages. They could wrap up the rest of the series in a single episode and GRRM can complete the books with a 10 page pamphlet.
It's the great conundrum of fantasy literature, finding balance so that the story doesn't rely too heavily on a single creature, weapon or magical ability which then solves things too easily. And pretty much every single epic fantasy book or series has botched it. So GRRM and the showrunners are relying on the tenet that Dany doesn't want to conquer a kingdom of ashes and won't use the dragons to take back the Iron Throne. But even with that they can't get around the fact that there are 1000 other non-violent things the dragons could be doing to help Dany win.
That kind of leads me to believe that maybe there's some truth to the theories that the Nights King manages to somehow kill one dragon, raise it and control it. It really helps balance things out and 2 dragons to 1 is better for the story than 3 to 0. Or what the hell, maybe Cersei somehow gets control of a dragon too so that all 3 sides have one.