Billions of people don't use calendar apps so they're useless; just remember your meetings.

Billions of people don't use todo list apps so they're useless; just remember what to do.

Billions of people don't use post-its apps so they're useless; just remember what you're going to write down.

Billions of people don't have cars; just walk.

You can dismiss any invention since industrial revolution with this logic.

The point, as I noted below, is that this is an impractical solution.

You can justify the value of any ridiculous invention by comparing it to a world-changing invention.

You have soundly defeated that strawman, well done.