I understand that sentiment, but look at how dressage is weighted and scored these days.
It doesn’t matter how much (correct) training and understanding the horse has. If he is an average moving horse (or less than average), he has no hope of being competitive. Should he not compete?
The weight of scoring shifted a long time ago to favor fancy movement over correct training with the introduction of Paces as a collective mark. By default, movement should (and is) already factored into each movement score. We did away with the individual collective marks recently, because horses with better movement but not necessarily better training were coming up miles ahead score-wise.
My seasoned event horse, with solid dressage training, is being outscored by my barely broke, super green WB. I can pull her out after weeks off and “phone it in”. She is GP bred top and bottom with all dams/sires on her first page having GP careers or producing horses with GP careers – so she is bred for dressage. Her natural suppleness and movement make her look way more trained than she really is, and it really masks the incompleteness of her training. She is much greener than you would think, yet scores well. As her rider, I’m blown away by it. It feels disingenuous especially when I think of how hard I had to work for a 30s score on an average or ok mover.