I’ve held off on replying because my opinion is fundamentally negative - but I don’t find dressage necessarily more abusive than other disciplines. I also agree that it’s not necessarily beneficial to be comparing to other disciplines - dressage should work on itself, as reining, eventing, H/J, and every other discipline should.
I think we can all do better. The one thing that is more obvious in dressage than most other disciplines is the amount of distress signals and unhappy body language that is front in center in dressage horses as they trot down the centerline. Most of these signals/behaviors are ignored or written off because the rest of the body appears loose or extravagantly moving. I haven’t enjoyed watching many UL dressage tests in a long time, because they show tense and unhappy horses even when they are well-rewarded and beautifully ridden.
There is a culture in dressage to completely ignore these distress signals, including in dressage meccas like Welly or Ocala. There are dozens of products out there meant to inhibit or reduce the expression of these signals - like the Tota-Comfort Noseband, or big cavesson/chin pads, etc. I think in this sense, dressage could do better in shifting their culture to be more sympathetic to listening to the horse, rather than trying to hide or disguise the signals.
It’s a tough question. At what point does an unhappy horse become a welfare issue?