Gems of War mostly chooses to be fully random.
However, it’s completely legitimate to have a game that isn’t fully random. There’s a randomness spectrum, from fully scripted (eg: the story quests) to partially predetermined (Explore teams have restrictions and an algorithm).
Human curation makes a lot of sense with certain things, like Campaign Tasks, precisely because weird situations can occur. Currently, the last week of Campaign 3 was precisely the worst possible scenario, but if there were another multi-day task, it might actually be impossible to complete the Campaign. You can certainly program rules for this, but nothing beats a quick glance by a knowledgable human.
From a developer’s point of view, RNG is a choice, not a necessity.