You do realize that every company so far has been doing that to every booster for every launch, right?

There's 2 options if you don't want to drop stages back on earth. You don't launch, you land the stage.

SpaceX is the company that pioneered propulsive landing of a booster. You can say a lot about them but not that they pollute with dropping stages in the ocean. Even in absolute sense that doesn't happen often and that's ignoring that they put over 90% of all the weight in orbit nowadays

Polluting with what? It's mostly stainless steel and other inert materials.