Every feature you ship increases the complexity of your system. Not just the code. The interactions, the edge cases, the things the support team needs to know about. Every feature costs complexity, and the budget is finite.

Most teams track velocity but not complexity. They know how fast they're adding features. They don't notice that each new feature takes a little longer than the last one, that bugs cluster in areas with the most interactions, that onboarding new developers keeps getting slower.

I think about complexity as a budget. You have a limited amount you can carry before the system becomes unmaintainable. Every feature is a withdrawal. If you only withdraw, eventually you're bankrupt. The system still runs, but nobody can change it safely.