I mean, it's going to depend on the ingredients etc. as to how good that specific food is.
Theoretically it would be possible to meet piggy nutritional needs without pellets, however you would need to have a very large working knowledge and in depth understanding of nutrition and requirements so as to get things bang on. Without fortified pellets there's less flexibility, room to be slightly less than perfect, especially taking long term health into account. I wouldn't recommended it for anyone who isn't experienced and very knowledgeable about species-specific nutrition.