Many meal-shake type products are made with whole foods, have sufficient volume to be filling, and have tons of fibre. There are even some companies (e.g. Huel) that sell what are essentially dehydrated, fortified meals, which provide some variety and also involve chewing.

In the context of nutrition and physiological wellbeing there's not really anything wrong with these products, and most are going to be better than a typical diet in many parts of the world. The issue, I would guess, is that the good ones aren't cheap.