Not only does Reagan have the same design problem as LGA and SFO (built before jetliners, runways too short), it’s incredibly close to restricted airspace. No civilian needs to fly into an airport that close to DC.
Travel in/out of IAD from DC can take an hour, which is obviously why people there prefer DCA. And the flights there are all short-haul anyway, so many are the types of flights people are doing on short turnarounds.
Immediately after 9-11, lots of people talked seriously about whether to re-open it. Ultimately they did, because Congress wants it.
The pain could be mitigated somewhat by adding seating areas and more aircraft parking while using larger planes. For instance, fewer flights total, consisting of 737s and a320s and eliminating flights that previously used shorter commuter sized aircraft.