Prior to this, the USA did not have the capability to transport astronauts to orbit without working with Russia, and if Russia were to just decide no longer to cooperate for arbitrary diplomatic reasons, we'd be screwed. As you know, the shuttle program was halted some time ago and the vehicle was a total cow the whole time it was in service.
So whereas this has been done before on a technical level, this represents a substantial increase in the USA's actual present space capability, and a major step in reversing the decline of the USA's competence in space.
737 first flight was in 1967.
Both B-52 and Tu-95 first flights were in 1952, both still in service today.
Sometimes problem is solved, and there is no need to solve it again, it would be insane for Russia to abandon Soyuz and develop something new at huge cost.