I will say that as I read everyone’s comments about people importing horses (or looking for horses) of higher and higher quality and that those are required to win/place/do well, I find that this really doesn’t relate with my personal experience - it could be a matter of region, judges, or something else that I’m not taking into account.
I showed with a trainer in the Midwest before judges like Janet Foy, Axel Steiner, Linda Zang, and Gary Rockwell for the better part of ten years. Her rides were almost uniformly thoroughbreds (with a quarter horse thrown in for diversity) - I had a thoroughbred (who I had purchased as an event prospect). I can’t remember a single show where we were ever really blown out of the water by fancy imported horses, or warmbloods bred to the nines in North America. They certainly are around! But it never felt, to me, that I was doomed to place behind them (or they were a shoo-in for top scores).
It was especially apparent with the more experienced judges - the average class scores (looking at training and first level classes, where I spent most of my time) might be lower than I could find in a non-recognized show (or a smaller show) but the people who scored highest of the competitors were the ones that put together a complete, mindfully ridden, correct test.
I would strongly disagree with the commentary that imported horses are responsible for the decline of dressage (if indeed, it is), or even that the warmblood-import market is related to the soaring costs of purchasing/ownership. I think there’s a lot of components behind that (which may be worth another thread, I imagine it’d be a really interesting discussion) but not really fair to blame it for the decline in dressage.
Some of the factors that I think are more likely culprits: trainer accessibility. People have talked about dressage specific barns, which I think might be worth expanding on. Despite being a dressage rider, I’ve never been at a barn that was “a dressage barn”. I rode with a trainer who got started in eventing and switched to dressage later in life when her event prospect sustained an injury that made jumping impossible. I think we need more trainers like that - maybe not a fundamental “niche” dressage rider, but someone who has solid, fundamental basics and who can start students and horses correctly. Riding with her has always been so affordable (a training ride is $30, a lesson is $35 for 30 minutes, and they often run long) and it’s made it easy for her to introduce other students to dressage as well.
This might also be an answer to the issue of some people being priced out of the discipline. You don’t need a big name trainer/coach, or a big name barn, or a big name breed horse to go, ride a good test, get good scores, and feel like you accomplished what you came to do. I think that by the merit of how the horse industry markets itself though, the big names tend to get the majority (if not all) of the press so people fall into the idea that they need a dressage-only barn, trainer, dressage-bred horse, to succeed.
(Also: I would ask if winning a class or having the highest score is what succeeding in dressage is about. Is it fun to win? God, yes, absolutely! But I never felt like dressage was about comparing my ride to the person before me or the person after me - it was about me going out and putting down the best test I could, especially compared to prior tests I’ve ridden. Is that passé now?)