I've had a very similar experience. Ironically, simple frameworks like WinForms, or tools that promise easy and rapid development, often turn into the absolute worst-case scenarios for maintenance.

This tendency is especially strong in code-behind frameworks. Because the domain logic directly relies on the state of UI controls, the business logic becomes entirely entangled with the view itself. And what is the result? Every single architectural layer ends up stuffed inside a specific event handler.

I could understand if this came from a small outsourcing shop, but what baffled me was that this was the codebase of the top company in the world in that specific domain.

And to top it off, you sometimes have to integrate with an SDK where the methods are literally named function1, function2, and so on. It is always a thrilling experience.