Dressage isn't dressage until you are doing something all riders don't do. If I W/T/C my horse, teach her various cues, etc, I'm simply riding her. When we trotted and cantered in circles today, we were not doing dressage. All riders sometimes circle their horses.
Now, if I'm doing a circle and someone is worried about HOW she does that circle with an eye toward building to a high state of collection, THAT would be dressage - because the training is to achieve a goal that is consistent with dressage and almost no one else. When Trooper or Mia & I do circles, my goal is a balanced, relaxed horse. A dressage rider considers that a transition stage, while I stop there.
I have no interest in the goals of dressage. I don't want to use a system of training that is designed to achieve the goals of dressage. It gets back to having terms that are meaningful. If this is dressage:
Then what word do we use when we want to describe this:
If I reject the goals and system of dressage - which I do for me, since it isn't relevant to the riding I want to do - then why is riding in a circle dressage? Why is moving my horse laterally while we also are moving forward 'dressage'? And what historical myth gives rise to the idea that dressage gets to define what was being done before dressage existed?
I can't stop someone from using dressage to mean 'all riding', but it robs us of a word to describe dressage. It also makes the user look stupid, since they are describing what existed long before there was dressage.