Once you scale past simple prototypes, you need performance and new features. And the architecture stops being simple and complexity eventually creeps in.
I’ve implented 4 iterations of a product from scratch, and eventually they all get complex, even though each one started out with the goal of being simpler than the previous iteration. Yes, iteration #4 is more complex than #1, but it is more performant.
In parallel I’m building a new house, and each iteration of the plans is more complex. You try to manage compromises. You take 2 steps forward, one back. Which way do windows face, can an older person navigate, is there enough storage space, cost, esthetics, where does a dirty dog enter, where is the chimney for preppers, driveway and orchard, septics and wells, drainage and water collection, guest rooms and hot tubs, all on a budget … Simple wont do.