I've been trimming my own horses for years and they are sound trail horses, that are ridden several times a week for 3-5 hours at a time. I think owners are very capable of trimming if they are willing to learn. In many cases, they have the potential to be better, because they care about their horses and they aren't in a rush.
I started out with a Farrier Science course (check your local community college), then rode around with a farrier, then progressed to trimming AND shoeing my own horses. That went along great for probably 8 years until I had some health issues and just wasn't able to shoe anymore.
I tried hiring a couple local farriers and wasn't impressed with any of them. (One thing you should know is it isn't even required for a "farrier" to go to school here in the USA, so you don't even know if the farrier you are paying has much experience or training- they could be anybody). So I thought, well, maybe if I could just shoe the fronts, it would be less work.
So I started researching barefoot horses and found out that not only was it okay to ride them, but it was considered a lot healthier (something I also learned in Farrier Science) and that I could use hoof boots if needed in the rocks.
So I ran with that idea and have been happy ever since. Horses are sound and healthy. I'm happy and don't ever have to pay a farrier. Don't ever miss a ride due to a lost shoe, nothing!
So I don't think I will ever go back to shoeing my horses. I see no reason to. I trail ride and I can do that perfectly well barefoot, or with boots. Boots are just removeable horseshoes after all.
PS. I think the secret to sound barefoot horses is never take off any sole (unless it is flaking off already), and keep the feet as dry as possible.