AS - You probably picked the worst trail around here for your example. VDOT doesn't have money for maintenance outside of the actual roadbed. They don't even mow the medians anymore.
The trail along 123 is much better maintained. I think a lot more people use 123 vs 7100, so they try to keep up appearances.
W&OD, Custis, Four Mile Run, Mount Vernon, are all in much better shape. I like the trails that connect to Wakefield and Lake Accotink (gravel but not bad).
Some good choices across the river, too. Capital Crescent, Rock Creek (but not near the zoo), C&O, Metropolitan Branch, Henson and the most of the Anacostia trail system.
Don't limit yourself to the trails. There is also a good system of rideable roads.