Starlink satellites will eventually de-orbit by themselves. The low-orbit altitude they fly in is not a completely vacuum. If they aren’t reboosted drag will slow them down enough that in about 5 years they come down and burn up in the atmosphere. We should worry more about those satellite in higher altitudes, like those TV broadcasting satellites that are in a geo synchronous orbit. Those will never come down without human intervention, but they are so far away that it’s difficult and expensive to reach them.