Do you ever feel like your Reddit post fits the topic but not the community ?

i usually read a handful of recent posts and comments to get the tone, then ask whether my post would feel useful to that community

Reading recent posts helps, but I'd go one step further: sort the sub by Top > This month and look at the format of what's winning there. Title style, length, whether people use images, story vs data. Two subs can share a topic and want completely different posts. I take the same idea and rewrite it per sub instead of cross-posting the same text everywhere, and it does way better. If the top posts are all memes and personal stories, a polished guide just won't land there.