Let's be brutally honest, the problem didn't occur overnight, it's been growing for decades. For decades the answer was simly to add another lane to the beltway, then they got the idea that maybe the feeder roads needed to be improved. The government hasn't led, they have been behind the curve.
What have they done? Sell off railroad right of ways and rip up tracks Commuter parking lots 45 minute drive away - now in the middle of the congestion. Call it concentrated congestion.
There is no practical way to add a bus lane to 5/301, but some half baked politician throws it out there.
5/301 is not a limited access highway. You have traffic at intersections making both left and right turns.
They have already expanded those roads and they are still congested, construction or restriction of a lane would only make it worse.
Sorry, but this is a long standing problem and mostly what we get is a lot of talk, grand plans with no funding (for good reason).
But mostly it's becasue the tri-county area, most of it, is found to be not worth serving. It's left to a few private bus companies to run "for profit" operations. Very little in the way of competition either.
Between work travel and where I've lived, it's more common than not to extend commuter rail service to the outlying suburbs - even light rail.
The upside, decent all weather transportation (if maintained); you can move a lot more people at a lower cost and lower carbon footprint.
The downside: Capital investment for construction and acquisition of equipment; grade level crossings which pose.; long term solution.
It's not unique, DC and Baltimore already have service, it just doesn't head south and east.