NASA is still doing the hard/interesting stuff, but now that there is a market that can more cheaply/rapidly work on creating the rockets/vehicles to get payloads where they need to go they can focus more on the actual missions.

Likewise, NASA has always chosen "buy" over "build" where applicable (like contracting out spacesuit construction to major textile manufacturers). If they'd done everything in-house, that means fewer resources where it matters. Public-private partnerships make NASA more effective, not less.