Lots of people don't recommend adlib feeding now, rather that you should limit a baby rabbit's pellets to encourage good hay eating habits from a young age.
Wild rabbits wouldn't get a concentrated feed like pellets and they were introduced originally to put weight on to rabbits bred for meat - so a small handful is plenty, just to provide your bun with a set source of vitamins etc and then hay/grass/veg should be adequate to meet the rest of their needs