For any given piece of crap, there's a demo that makes it look pretty good.

One of the reasons you should use the system you're building for real and not just demos.

If you only demo, you'll be drawn to the parts of it that demo well and work, and away from the parts that won't.

You'll erroneously conclude "this kind of works," but it actually doesn't.

You're just focusing on the parts that look like they work.

As you avoid the parts that don't work, those parts become increasingly in your blind spot.

They become invisible to you, even if they're huge.

Whereas if you use it for real, you focus on the parts that you need to use, whether they work or not.

When you try to interact with a part that doesn't work, and are in a position to fix it, the system gets better and more capable the more you use and improve it.