The skill of the rider matters incredibly. In fact that’s one of the reasons that the top equestrians compete well into middle age; riding skill continues to grow through middle age and so it’s one of the few sports where top competitors actually improve as they go…
Ummm, okay, so what they’re saying is that it’s hard, fair enough.
It’s also really hard to hit a 95 mph fastball 400+ feet, but baseball isn’t an olympic sport.
You know what else is really hard, controlling a car that’s going 150-200 mph for 3-4 hours on a track with 60 other cars, still not an olympic sport.
It’s also really hard to hit a small white ball straight down the middle of a fairway, golf still isn’t an olympic sport (nor should it be).
If dressage is an olympic sport, why isn’t Horse Racing? I suppose some might call the Steeplechase a race, but it’s not. I don’t care how much control a rider exerts on the horse, it’s not a sport.