When GetIt Package Project Dependencies first came out in Delphi 10.1 Berlin, they didn't work right, or at least not for me in the way I expected them. I had problems with them in Delphi 10.2 and 10.3 as well. I don't remember if I tried them or not in Delphi 10.4. However, with the new Delphi 11 Alexandria that was released last week, they DO work! Yay!
The idea is that if a Delphi project use packages in Embarcadero's GetIt Package Manager, you can list that package as a dependency in the project options. When you try to compile the project, if that GetIt package is not installed, it will put up a message prompting you to download it, then continue building the package once it's installed.
That was a great idea but didn't work very well. I always had to halt the build process, manually install the package, then come back and start the build process again--a minor annoyance but still, it wasn't smooth. Now, with Delphi 11, it is a smooth process: I get the prompt, install the package, and Delphi keeps right on compiling--sweet!