Do it because you want to, not for other people.

Do it for yourself.

I once undertook a project for personal use that I knew could be useful to many people (it was for a game).

People were getting interested in using it even in its earliest, experimental, pre-alpha, prototype, whatever-you-want-to-call-it, stage.

But then the unthinkable happened: I quit the game because the dev was irresponsible and was largely perceived to be unserious and lazy, when this game is his main source of income as far as the community knows.

So I of course lost interest in the project as well and abandoned it.

If I was doing this for myself, it wouldn't matter at all, but some people were interested in it, some were using it, and even as recently as last month I had people message me asking if the project was ready or how to use it. (the project was started in Jan 2024, I quit in Feb 2024)

The point is that if you're doing it for yourself and you quit, it wouldn't matter, but it can almost feel as if you're letting people down when you do it for someone else rather than yourself. So do it for you. That way, you won't have people's expectations weighing you down. If you can't work on it this week, it doesn't matter. If you can't do this feature for xyz reasons, or because you don't want to, it doesn't matter. Because you're doing it for you.

Or at least that's my take on it.

You mean RPL? There are lots of interpreters for that already. That's the sort of thing to write because you want to write it, not because other people want it, unless you're part of a community that is asking for it.

If you just want to implement an interpreter because language implementation interests you, I suggest Lisp or Scheme rather than something like RPL. The book "Structure and Interpretation of Computer Programs" explains how to do that and it is great. You can read it online at mitpress.mit.edu/sicp .

That seems like a fun project, I have myself written two interpreters/simulators and one compiler and it's a lot of fun. However, that's something you do for your self, without a ton of effort and dedication you won't make something useful