Simple architectures work well, until they don't. A good example is ye olde ruby on rails monolith. Dead simple to set up and iterate quickly, but once you reach a certain organization and/or codebase size, velocity starts to degrade exponentially
How often do you hit ‘that certain size’ when velocity starts to degrade anyway?
X works well until it doesnt… is not exactly a compelling argument. That can be said of simple and complex architectures, or just anything at all