Actually depends on the club. My running group couldn't care less what you wear. The vibe rule is for specific social clubs, usually the fancy ones. They want a certain look to keep the atmosphere. It's not a blanket thing for every group.
Oh man, my friend got hit with that last month. He showed up to his book club meeting wearing the wrong shirt, like just a plain tee, and the host actually asked him to leave. It was super awkward because he'd already brought snacks. They said it broke the vibe or something. He hasn't gone back since.