Dear Product Manager, a strong vision is the real core of the product

The paramount skill a PM needs is the ability to influence people. Talk people into jumping off a cliff on your behalf. To commit long hours to an idea or initiative that may or may not work. And when it doesn't work, to commit to tweaking and adjusting till it does. Or doesn't. :)

One of the things that makes influencing easier is when one radiates a unique contagious energy. A fire in the eye that you can project from yourself, infect everyone else with and ginger them into action. 

There's no better way to radiate such contagious and positive restiveness than to be driven by one clear sense of purpose and a big destination. An outcome everyone will like to see but which seems quite some distance off. Yet, almost touchable.

One PC in every home.

The end of all wars.

Colonization of Mars.

I can imagine the PMs using the "PC in every home" war cry to keep pushing the teams at Microsoft and IBM. To use that to influence product design, pricing, operations and supply chain management. Every release you ship that brings that goal closer, fuels the team afresh and pushes the team to even more improvements and productivity. Well, there's now a PC in almost every (middle class?) home. 30+ years later.

So, your product is not the mix of features you have thrown into it, nor how you are communicating it to your market at the moment. The real centre of your product, is that vision on which it is built.

That's your north star. Let it guide you.