Recently switched jobs from maintaining a 15 year old Windows Forms .NET Framework legacy codebase.
At the new job we stick to Clean Architecture, use unit and integration tests, have a code generation tool, actually make nice use of generics and use dependency injection. Also agile processes, automatic build tools, whatever. The difference is night and day and I'm so glad my ex boss fired me because I told him he's an asshole and his codebase is shit.