I am also guilty of it. I have been accepted as a writer for many publications but, so far, have probably only submitted stories to about a third of them. Mostly I am writing the things I am inspired to write, and then choose the publication that best fits the story. It's also about getting eyes on my stories. Yesterday I submitted a story to a publication that is new to me, but really ummed and arred over whether I should or not, because I didn't get the impression that publication has much engagement going on. However, I decided to after all, because it's nice to spread our wings.

I keep thinking I should look through all the publications that I am a writer for and write new stories based on what fits with them, but so far I am mostly finding that I just write what comes, without preplanning topics.

If you are looking for more people to submit stories then perhaps there could be a way of grabbing attention/incentivising? ILLUMINATION publishes a regular "welcome new writers" article, tagging all the new writers, and giving onboarding advice - it's clearly a pre-written article that probably gets updated now and then, and all that changes otherwise are the tagged writers. Perhaps you could find a way to bring attention to the first published stories of new writers, so that they know that they will get eyeballs on their stories. I would also be happy to pen something that could encourage new writers to publish in New Writers Welcome, if you would like - I have an idea brewing as I type.