I don't care as much about variety (a varied diet) as providing a suitable diet. Imo, there's an implicit assumption that a varied diet will be suitable simply because it's varied. That's a tenuous assumption since what is seen as "varied" to one person might not be considered varied to another. (And all this assumes we know what each fish consumes.)
E.g., someone might consider using 5 different fish filets (e.g., tilapia, cod, salmon, catfish, trout) as being varied, when because none of them are whole, may be a diet that lacks large amounts of key minerals and vitamins.
I have used various foods (crickets, earth worms, various pellets, shrimp, fish filets, etc.) but I've always felt a HQ pellet must be a significant part of the diet for most fish, (perhaps some exceptions being herbivores or picsivores that are fed whole fresh fish.