FAA stopped issuing waivers to the RSA standards a few years back and published Order 5200.8 in 1999 addressing the process to assess and address RSAs. Over the last several years, US airports subject to part 139 and FAA airport funding have worked to address substandard RSA. Some airports like, DCA and MDW were known to be problematic with respect to full RSA compliance. The availability of arresting systems EMAS have dramatically helped address these runway ends where airport geometry limits the space available for RSA extension. Simply reducing the ASDA is not always a solution, since by doing so one can make the runway not economically viable for air carrier operations.
To answer your question, RSA compliance is mandatory and FAA no issues waivers to the standard like they did in the past. All airports are required to come into full compliance to the maximum extent practicable and to develop a plan to do so. However, there will be some airports where full RSA compliance is not possible. Where DCA fits into this process, I don’t know.
Rich