There are lots of horses that are able to make it without supplements but imo once damage has been done you need to give the horse every opportunity to heal and a good hoof vitamin does that.
Founder occurs when the ecoli in the gut goes overpopulates due to sugar so a little cinnamon for a foundered horse imo is a good idea.
My Belgian mare was severely foundered and I had no idea just what a job that was to keep her going. In the end, I had to put her down.
My foundered Arab mare was middle of the road foundered and the farrier said that if I had not told him she had ever foundered he never would have known. It was a matter of allowing her to heal herself through diet and supplements. I try to post a pic of her, Daliia by Imperial Imdal. I had to leave her in Maryland with a friend because I had too many to move and I miss her to pieces. She wasn't broke to ride until 17 years old and I had her for 8 years. She had foundered before I bought her.