The real excitement and discoveries are all the result of unmanned missions such as the Voyager, Cassini, New Horizons, MRO, etc. missions (and the fabulously successful rovers). Manned spaceflight is just pork for Congressionally-powerful districts with no scientific return. The SLS (called the Rocket to Nowhere), the Orion capsule, the old shuttles, and the ISS are/have burned billions and do nothing for science....and they endanger astronauts.
The problem is that NASA is run by ex-flyboys and the districts that build their toys want the pork to keep coming. Bolden is a shill for the manned space lobby--it is fairly disgraceful how he has tried to kill planetary science.