It was sloppy coding on the project I took over, but it still made me wish for explicit style interfaces. Cleaning up frequently broke the project in non-local ways, because someone would break an interface without meaning to.
Unless you are doing some (possibly unsafe) magic the interfaces are strongly typed, external dependencies are locked, so one cannot really break an interface without meaning to. Or I guess without realizing it immediately.
With huge projects that pull in packages i have seen the dependency management become a mess but most of the time its not that bad.