Hi Matt, I started DC UL Backpacking a few years ago on meetup and then decided last summer that I would prefer to leave meetup and backpack with folks I personally knew who enjoyed 20 mile days and aggressive weekend trips to PA, VA, WV, etc -- some of whom are BPL regulars. DC UL Backpacking is still in the meetup community but you're right that the frequency of the outings is down. Of course, there are several other area meetups that cater to a non-BPL crowd and reduced mileage plan.
I agree that meetup is great but I grew fatigued with trying to vet new folks in advance to see if they were compatible with the group's style and, worst of all, I was very disturbed by folks who assessed their backpacking speed/stamina higher than reality warranted and either got themselves in over their heads on one of my trips or caused everyone else to go out of their way and accommodate at the expense of the group. (I'm not talking about injuries which can and will happen to folks but rather an inability to keep up with 3 m.p.h group speed in any situation.)
I encourage you to backpack with Ryan at DC UL Backpacking and if that works out for you and you want to join my non-meetup group of folks who know each other well, have Ryan or one of the other guys who knows me vouch for you and I'd be happy to include you on one of our trips that goes out at least once a month for 25-70 mile weekend outings based out of DC. (This isn't meant to be mean or exclusive -- I've just been burned too many times by folks who swore up and down that they could knock out 20 mile days no problem and then turned out to not have that ability.)