Hello!!
I believe as long as there’s no scabs/sores on the feet, it’s fine. The fur on rabbit’s feet often wear down with age, especially with some breeds more than others (I read something about lops having thicker hair around their feet? While rex breeds have thinner hair and sore hocks is a common problem).
If it looks a bit red, it might be irritated or inflamed… There is a way to treat it and get the fur to regrow (here) but some rabbits won’t tolerate the treatment (my bunny won’t sit still and panics whenever i tried to wrap his feet… so I gave up because I didn’t want to keep stressing him out.)
There are other treatments, like using getting your bun to sit on a towel damp with a diluted chlorhexidine solution (1 part solution/5 parts water)…here’s a video on that.
Before you try and treat it, I would recommend consulting your vet first!
If your rabbit gives you a hard time, you can always just make sure to keep his environment clean (change his litter often so he’s not sitting in damp litter) and try and prevent them from walking on hard surfaces (I’ve put lots of soft blankets all over the floor, it’s better than carpet). I sometimes take a damp paper towel and gently wipe their feet if you can to try and keep them clean.