[Kwpolska]

Java IDEs can debug third-party code just fine with decompilation. C# IDEs can get the original source code (https://www.jetbrains.com/help/rider/Debugging_External_Code...). Having to build all dependencies would be slower with no significant benefit, especially since the code compiles to bytecode, not native code. Forking is also doable, e.g. with an internal package feed (and you don’t need to integrate your build stuff with theirs).