Well, the first step is to not be an elitist gatekeeper who scares away any beginner who tries to develop open source stuff. Because even if their first few repositories were not exactly good, they may eventually get better, and if their experience with FOSS community was a pleasant one, there is a pretty high chance they will publish their later work too.

If, on the other hand, you publicly shame every mistake a beginner makes in hist first repository, they will probably never publish anything.

It's important to praise anyone who's self-less enough to write FOSS. Even if they aren't exactly good yet, just the fact that they have decided to publish it is really important. I'm not saying that we shouldn't offer any negative feedback - quite the contrary - but the feedback definitely shouldn't be public shaming in a meme post on random social network.