I think games like Fallout and The Witcher are just better games at their core. Destiny really doesn't have much substance compared to games like that. It has to rely on different mechanics like RNG loot to keep the player base coming back. Not saying it's necessarily a bad thing, just a different business model that we have to learn to accept in this modern gaming landscape. They can put out less substantial offerings and rest easy knowing that much of the player base is still here to collect stuff and develop their character.