A different approach maybe ?
I never joined a club at my fittest (18mph average over 50 miles) but sometimes got caught up in one and it certainly pulls you along, that really surprised me. But inevitably , if you choose the wrong group, you're going to get spat out.
So it occured to me, if ever I had joined a club, I'd have been happy to ride along, get spat out if I couldnt keep up...and accept it. Let the others do their thing, you do yours. You can still enjoy the remainder of the ride and gain from the work you put in while in the group.
Nobody ever said you have to start AND finish with the group.