Shoes are not for the horses health, in fact quite the opposite. They eliminate important shock absorbing and circulation features the hoof has.
It's all about having a horse in a stable 24/7.
All six of my horses are without and I show, no problems. It just takes some dedication and time to make them strong.
And if someone tells you that a specific horse needs to be shoed, they either don't know the hoof well or don't know of other solutions.
The only horses that should be shod are the ones that are stabled 24/7 and only for that reason.
I've been riding barefoot horses for 5 or 6 years. None of them has ever had any problem and we go on 30 minutes to 8-hour trail rides. They walk on grass, roads, rocks, mud, snow (even more than 1m of snow) and ice, they do dressage, show jumping, endurance, cross country etc and even competitions.. I've never seen feet that healthy!
But most of them live H24 outside (with a shelter if they want) on multiple different grounds so their feet can be naturally stimulated and healthy. They also have a professional take care of their feet every 2 to 3 months (natural farrier).
Since these days, i don't see the utility of shoeing horses. But i have to admit that some of them have more sensitive feet and can't easily walk on roads, for example. But in this case, i recommend talking with a professional (for barefoot horses) and maybe think about putting horse
You can know if the feet are healthy if they are not cracked and dry and if they have a nice even hair line and if you have nice wide heels and a big healthy frog and even walls and no bar to speak of. From what I have learned shoes are only good for your horses feet if your horses feet can't keep up with your riding, or if you ride on really rocky ground.