Just adopted a very sweet Irish Wolfhound mix. She's as dumb as bricks or just has no desire to impress us with any display of intelligence. I would be floored if she was able to produce any toy on command let alone a specific one, lol.
And yea, I agree that it's hard to know if the dog is just dumb, or independent and lacking any ambition to please us by learning "silly" games.
One thing one trainer I listened to said was that some dogs are actually more like cats.
That stuck with me, and I have kind of accepted that she will probably never be the kind of dog that follows my hints and commands blindly. The important thing is after all that she doesn't have any "dangerous" traits like aggression or being over protective.