Keeping a sensitive hoof sound can be a complex formula.
Diet plays a crucial role.
The rocky ground the OP's horse is on plays a crucial role.
Whether the horse is flat-footed or has a nice concave sole plays a role.
Keeping the horse structurally sound using a chiropractor plays a role.
Injuries to the skeleton or tendons can also affect the hooves because they affect how the hooves might need to be trimmed to keep the horse comfortable and ridable.
How good the shoer or trimmer is plays a role - not all shoers and not all trimmers are created equal, in spite of what they think of themselves
Some have a lot better gut instinct than others and, oftentimes, going strictly by the book or school they learned from isn't going to work.
I can give testimony to flat soles and diet. My 23-1/2 yr old was diagnosed as insulin resistant 4 years ago and underwent a severe/strict diet change.
He is flat-footed and always has been so I kept shoes on him, seasonally, back when we were hard trail riding (hard as in sliding down hills and digging up the other side).
Imagine my surprise and joy when, two years ago, he went hot-footin' 40' down the middle of our gravel drive and never missed a lick (he's a Tennessee Walker).
I wouldn't call his hooves rock crusher but, with diet and good trimming they have evolved to where he can now go barefoot over gravel and he never could before.
One would think that being insulin resistant, his hooves would be in worse condition but that isn't the case.
I have one horse who has a prescription for heel height and toe length from the chiropractor. Do anything different (shorter or longer) and I promise he's sore. It's a good thing I know how to trim or I would have a bloody fortune tied up in that horse's hooves.
He didn't used to be that way, but he fractured his sacrum four years ago and I am sure the change in what his hooves now need is due to that. He is only 12 but already has a Hunter's Bump over that area that makes me ill.
I said all that so say -- the OP's horse hoof condition can improve without shoes but it takes patience (at least a year), diet and a trimmer who actually knows what they're doing.
Don't give up on the barefoot route - try and find someone else thru recommendations in your area