They stretch their resources as thin as they can to maximize profits, it's honestly a basic business tactic. That's why the relic quest hasn't really had anything unique battle wise like Hydra created for it since the very first quest, it's all just currently existing content artificially extended with long grinds, kinda sad the relic questline was relegated to that one quest that will try to keep older content in circulation and somewhat relevant maybe even after the expansion, which is admittedly also kinda clever. That's why most of the other systems introduced are just click on thing and watch a cutscene. That's why even in Coil most enemies are just recolors or slight modifications, even if Final Fantasy has always had that since the very first one, but still. That's why most gear is full of recolors, even current top tier gear.

Lowest amount of effort for the highest amount of gains, or rather they allocate most of their efforts and resources into very specific major content, dungeons/raids and the primal battle of the patch always being their top priority, there's nothing wrong with that but ends up making the rest of the content being less than it could be or just plain badly implemented.