When the Spanish explorer Cortez landed on the shores of modern Mexico, story has it that he burned his ships to ensure they were "All In" on their conquest. This is a beautiful metaphor for building software products.
Many tout the benefits of both iteration and simplicity. The problem is that to iterate and preserve simplicity, features have to be cut. You have to burn your ships that got you to where you are. There is no turning back.
This can be tricky. You have to kill the features that individual developers and designers had personal relationships with, features that took careful planning and months to develop. They have to be swiftly killed.
It's the right choice. If they're not on the critical path to your best user experience, they have no business seeing the light of day.
It's tempting to keep that one cool feature, to leave that one option in the settings, to leave a little bit of product flexibility in case users want to do Y and Z in addition to X.
But remember - users will actually use the features you give them. If you include features that are "good" but not "great," some percentage of your users will experience your product as good and not great. Only great products survive.
Make bold and specific user experience choices, let them ripple though your product, and kill the features that are tangential.
By focusing on only one core experience, you have no choice but to make that the best in its class.
You have no choice because there's no going back. You've burned your ships.