I thought about creating something like that and the major problem that I see is that lots of meme templates do have copyright and the font that's typically used for memes, Impact, isn't free either. Well, and it isn't done by merely developing a software and offering it for download. You would need to host the meme templates or some editor webpage, which is a whole 'nother skillset.

If we say that users bring their own meme template, and it can be a free font that looks similar to Impact, and it's not to be hosted as a webpage, then it would be quite doable.
You would "just" need to call the ImageMagick library with the right parameters. Still not trivial, but the path to get there is fairly straightforward. I could imagine that something like that already exists as an open-source project...