Your analogy doesn't make sense. You are getting benefits from using the shopping cart and you bring back as it's expected as part of the exchange. You bring the cart back to where you took which is a low effort commitment entirely proportional to what you got from it.

Free software developers are gifting you something. Expecting indefinite free work is not mutual respect. That's entitlement.

The common is still there. You have the code. Open source is not a perpetual service agreement. It is not indentured servitude to the community.

Stop trying to guilt trip people into giving you free work.