Came here to say this as well. LEGO Kits simply show you the 'happy path' if you will, but it's also designed for you to take it apart and remix it however you will.

Your LEGO analogy is thus unnecessarily limited, because looking more into the design philosophy of LEGO also uncovers even more clues as to how to build great design systems.
First is encouraging and enabling the creativity of the designer/builder. Giving them the tools to create (via the constraints and initial directions). Then helping them realize that the instructions is just the initial template, not the end all be all. This knowledge is a sort of psychological safety net, which we know is important for creativity.
As you said, contribution is an important part, you can mix and match your LEGO kit with others to produce even bigger and better things, but it also shows you how to discriminate between those different kits and where to use which appropriately (example, two kits might have different doors, but one door is preferable because it is better for this build, while the other can be used for a back door or just left out). It teaches you to pay attention to context.

Probably a few other things I can pull out but now I'm probably taking this too far 😜.

Still learning about design systems myself, so thank you for the article.