Can someone help me understand? Maybe my understanding of contracts is too simple but in this example:

I’ve developed and published a unity game. The game is complete and will receive no future updates from me, but will remain on sale for the foreseeable future.

My understanding of the current situation is that unity is somehow claiming these new terms will apply to my game. But I don’t see how that’s feasible. Shouldn’t my relationship with unity be at an end as the product was completed? Would I have to de-list my completed game to avoid charges? How is that legal?