That's a short-sighted statement that tells none of the actual story. The NTSB's job is to recommend regulatory action to the appropriate agencies - USDOT, FHWA, FAA, etc. Those agencies almost invariably adopt those recommendations.
Some recognizable regulatory efforts that the NTSB has been responsible for, in spite of having "no regulatory authority":
- TCAS
- GPWS
- Wind Shear Detection Systems
- Aircraft Lav Smoke Detectors
- Graduated Driver's Licenses
- 21 year-old drinking age
- Air bags
- CHMSLs
- CDLs
- Positive Train Control
To dismiss the power exerted by the NTSB is just stupid.