When you say complete pellet-based diet, do you mean no hay?
When I say complete pellet based diet, I don't necessarily mean no hay. Some pellets are labelled as a 'complete diet', such as Purina, Manna Pro, etc. They have all the protein, energy, vitamins and everything that a rabbit needs. You can feed grass hay with them if you want to give your rabbit more fiber (especially for rabbits prone to GI issues) and/or something to chew on. The complete diet should have enough fiber and hay material ground up in it to cover
most rabbits' nutritional needs, but those needs vary between breed and between rabbit. (If I was feeding a holland lop, for example, which tend to be more prone to diarrhea and digestive issues, I'd almost certainly supplement these pellets with a grass hay).
Personally I rarely feed hay and my rabbits do great (although they are intact, breeding rabbits, so their nutritional needs are quite different from spayed, pet rabbits which tend to have lower protein and energy needs). I haven't had GI issues, teeth issues or other diet related issues on my current feeding plan and I've been feeding it since 2012. (no "GI stasis" - that doesn't have to
When pellets get a bad reputation, it's often because of the low quality pellets sold at most pet stores (especially muesli) which is marketed towards uninformed consumers and usually not meant to be a complete diet, so they lack many key nutrients. It can be
hard to find a pellet that actually covers a specific rabbits nutritional needs, and the quality and freshness of pellets varies so much by location that finding information online isn't very useful. That's something best asked of a local rabbit expert.
Not to say pellets are the only way to feed a rabbit. There are many correct ways to feed a rabbit, as long as they get all the nutrition they need. It's just the one I personally find easiest and most consistent, especially as its difficult to find good quality greens & vegetables around where I live.
