If you haven’t started it by now, it’s probably time to forget about it.
You’ve most likely built it up so much in your head that it’s not an idea any more. It’s a dream.
And dreams no longer work in real life.
Instead, it may be time to start getting things done. To start smaller, easier projects. So that you can get used to the feeling of starting (and failing).
If you’ve created a dream, that’s fine for entertainment. But if you want to really change the world, it’s time to start.