I have never played a sport outside of gym class. When I went to local sports meetups, I mostly found people practicing the sports they played in high school or college. I sucked by comparison, and it showed.
I think this is the key here. You're going to be the FNG (<expletive> New Guy) for a while. So choose your sport and level wisely. Most leagues that I have come across have at least two, if not three or four, levels. Where, say, the "A" level is for folks that played in high school, maybe even college, while the "C" level is going to be accommodating to someone who is just picking up the sport as an adult.
And really, sucking at the sport could be advantageous in terms of socializing. "Hey, anyone want to run some skill drills next Wednesday evening? We'll meet at <local park> at 6:00 PM, practice for an hour, and if anyone's up for it we can go to <pub next door> afterwards." Yeah, you might only get one or two takers if most of the folks have kids but that's just part of adult socializing.
However if you're the only one who comparatively really sucks and maybe on top everybody else is treating things a little more competitively, it possibly starts feeling a little bit too much like gym classes at school, where you always got selected as one of the last ones into a team because everybody knew you weren't really the sporty type and consequently wouldn't really improve any team's chances of winning…