I think the problem is that most people at least have a reasonably clear idea on what colonising Mars would look like. I doubt that there's two people on Earth who agree on exactly what a todo app should do.

If you believe a perfect todo app is possible, make one. You'd get rich.

I've resorted to writing my own because I've never found one I'm even remotely happy with. The requirements are too personal.

Meanwhile, getting a working definition of what "colonising mars" means is reasonably easy, even though people mighty disagree about the details.

Which bit are you disagreeing with?

That we can mostly agree on what a Mars colony would look like or that no-one agrees on what the perfect todo app needs to do?

The perfect ToDo app looks like this:

A personality profile that identifies which ToDo app you should use.

It really isn't.

It's hard to say when neither has been done yet.

I'll believe that if someone manages to make a perfect todo app before Mars is colonised. I very much doubt I'll see that happen.

In that case I'm all for a future with imperfect todo apps.

Perfect todo app is simple: a text editor. Each line is a thing to do. Done.

Works for me, anyway.