You can't save the world: mission statements that help you build
One of the most helpful tools out there for building is a really durable mission. Good ideas and asks create an endless backlog, and a mission helps you understand the roadmap journey you're actually on. It helps you solve for "it's this, not that." Often when I join a new company, I find no product strategy at all, and coming up with one is my work. One reason I think strategy has been so elusive for these companies is the lack of a good documented mission. So that's where I usually start.
You can use Simon Sinek's Start with Why framework, and there are probably loads of others. But a simple way to pressure test your mission is to iterate until each of these parts sounds usable and right:
Mission Statement: To [action] for [target user].
Is feature X helping [mission statement]?
Our North Star Metric is [user of mission statement] that [action of mission statement].
A measurable outcome
I think it’s okay that many mission statements will require a separate, internal definition of the action verb, of what counts and what does not. But the verb should not be an unmeasurable one. For example, if you don't literally intend to measure innovation by patents and you really mean "I know it when I see it,” then “innovate” a bad action verb.
At one point during my time at JW Player,—this feels okay to name because it's years and years later and not even the same company anymore,—our mission was "the future of video." You could maybe ask "is feature X the future of video," but it's definitely not something you can measure, and I remember pushing back hard at the time because of how useless it was.
But don’t compare
Avoid mission statements that require a hard-to-measure counterfactual, like what would happen if they didn't use your product. "To have a better vacation," for example, creates a really strange comparative. Words like reduce, save, prevent, accelerate, and improve all imply you need a "before," or an alternative running in parallel like an A/B test. That may sound easy to measure, like X reduced by 30%. But without a real before, any amount of X counts. Now you're arguing that every little bit gets you there, and you end up flying around the world in millimeters. It also sets your mission up as a competition, one you're running against third-party benchmarks whether they exist or not. It's not inspiring to work toward, because you never feel like you're achieving anything in your own right, only staying ahead of a fictional opponent.
Connect to monetization
Another test is whether the mission connects with the monetization model. That is, there must be an implicit "the more units go up, the more the mission gets achieved." If the mission doesn't get achieved the more you sell, that's a mismatch, and one or the other would be best if changed.
For all of JW's mission-definition issues, they did connect monetization well, which was based on the video play. The more videos viewers start (and watch for about 10 seconds), the more everyone wins. Our customers monetized their videos most often with one ad at the beginning of a video; it wouldn’t make sense to charge some abstract price per GB streamed or hosted, or even minutes watched.
From their mouth to your ears
The mission has to be elemental. It's something you actually want to happen, and the reason you're building the thing in the first place. What is the outcome you're really aiming for, besides becoming a gazillionaire?
All you have to do is ask a founder, have them talk for a while, and you’ll get the answer. It's just that most founders won't and don't lead this exercise. It has to come from a function, typically marketing or product, that really needs this information to build upon. It's also hard to do this yourself. It's way better when a less-interested party interviews you and crafts the story from there.
How it helps
A directional mission statement is a great way to measure the product itself. Have you done everything you can to achieve the mission for your users, or is your product becoming a sprawling everything store before you ever get there? And when there are too many options on the table, or the choices are too vague, a solid mission statement narrows them in no time.
This isn't to say you eliminate all work that doesn't directly impact the mission. But nothing is a better intro to understanding tradeoffs than "is feature X helping us [mission statement]?" At least if it's not helping, you can have the conversation about why.