How would I explain this games never changing formula?

[Kallera]

I doubt we'll ever see any drastic changes to the formula. SE won't want to risk a huge overhaul after their smaller experiments like Verminion and Diadem didn't take off.
Most likely we will continue to see periodic additions of new content alongside the basics.

I don't mind it myself since I enjoy the staple elements like dungeons, beast tribes, story quests, ect. I do hope that future experiments like Deep Dungeon are successful as more content is always welcome.

Changing the layout of dungeons past the "3 groups of mobs and a boss, repeat three times" shouldn't be rocket science. and if this is the content they want us to run 90 times before the next patch, perhaps adding some changing elements to it wouldn't kill the game.