The natural ability isn't hard to find (though the exceptional horses are unique). I think that there are lots of horses who could be competing higher and more successfully than they are with their owners. It's the owners/riders that make the horses what they are.
However, the point I was trying to make:
The horse has the ability to go the Grand Tour, be it Power Prancing or whatever it is SS people show their horses in.
I've never had a trainer tell me that I can't ride my horse, though I would never claim that I've gone at it alone. I have had countless hours of lessons, the patience of nice schoolmasters, coaches at shows helping me enter the right classes and navigate the warm ups when I was just starting out.
However, I am more interested in exploring the mindset of having to relinquish control of your animal to a pro in order to achieve.
Do you still have to be able to really ride when the trainer puts all the bells and whistles on the horse?
This is also not meant to know people who buy made horses.
After all, not everybody is a trainer, and where would the the prospects go, if not to these people? (I am sure the kid who rides Totilas now has paid his dues, having heard his stepmom in interviews on how her riding was formed. certainly no free rides on the farm!) it's not better one way or the other.
I am of the 'can do' mind set. (sounds weird when I consider that I lack ambition...)
I don't think I would handle it well when a trainer told me I could not ride my horse....