That's the problem with sharing incomplete games. No matter how many disclaimers you put up, players will assume that you must be an incompetent designer, rather than that you didn't implement everything you were planning yet. That's not against you personally, I likely would do the same if I didn't have this experience. It's just inevitable I guess. Maybe I should have recommended watching the gameplay video first, which amounts to a tutorial. But then I would get less valuable information of how precisely players suffer as they play.

All levels are unlocked from the beginning. (There's the assumption that I must be incompetent.)

For anyone actually learning a topic for the first time, the gradual progression is necessary. In fact, I cut it short to not bore players with the demo too much. But I still needed to demonstrate an effective progression.

Of course if you're playing something that teaches you what you already know then it's not going to be fun or interesting. If you already know basic addition, then not learning anything of value and not having fun is the expected outcome. If you give this demo to young children, it might make them cry, but at least they will learn a little bit of addition. It's just unfortunate that I have to begin with basic addition because mathematics is built on other mathematics, mostly going back to counting and addition.

From what I’ve seen of “learning games” those past 3 decades, they’re not fun, they’re not really games, they only pretend to to either attract parents to buy for their kids, or to lure people who like games (usually disappointing). Or they’re not really about learning, they’re games pretending to be educative.

I agree with this except for the part that they're not really games. Of course they're games, just worthless games. And of course all games are learning games, because you have to learn to play the games you play to play them. So what's called a learning game is a game that you supposedly learn something other than the game you play by playing, which is nonsense, hence their worthlessness.

The making of a good game, and the making of a good learning tool, may be fundamentally too different to be compatible, or people are just bad at mixing them, save maybe rare exceptions.

But good games are of course good learning tools for learning to play themselves. With this insight, you can begin to understand how far simply mechanizing mathematics can go toward learning mathematics efficiently. (Read my book for more!)

FYI, for me as a designer, talking about your experience is helpful, but advice isn't. (This goes against frequently heard calls for "constructive criticism". Regular criticism is preferable to me.) Thanks for the feedback to the extent it recounted your experience!