Well, if you are making progress then you have evidence that it is not a waste.
It may show you are lacking endurance, depending on what you consider to be lacking. You have the endurance to do 3 sets of 5 squats with 10 minutes rest and lack the endurance to do the same thing with 5 minutes rest. If that is important to you then deload and force yourself to only take that much rest when working back up.
It isn't an objective problem though.