The existence of the NTSB under DOT, and the FAA under DOT and NTSB is itself a huge issue. So many unnecessary layers of bureaucracy. What do highways have to do with aviation? Nothing, water ports? Nothing. Etc.
Safety in each realm is entirely separable and should have remained so. DOT should never have been created. All that DOT does is slow and obfuscate anything the FAA might do. Also it allows nefarious actions like burying a rule making process. An example of this was when the FAA sent a proposed medical reform rule change to DOT. Its simply died there without further comment or action. That was probably what the FAA intended, since it was well known the FAA actually opposed any liberalization of medical certification. It was a sort of “good cop, bad cop” action. So DOT diminishes accountability by obfuscating responsibility. What is needed is a more focused and competent FAA, not more layers of bureaucracy. DOT should be broken up into smaller spheres of responsibility, i.e. highways, ports, FAA, etc. Each of those to be entirely accountable within their sphere.