There's a well-worn saying in the world of politics: "All politics is local", spawned by former House Speaker Tip O'Neill, who explained that a politician succeeds by understanding the needs of the people who voted them into office. What directly impacts the individual's happiness and well-being will almost always trump a more philosophical issue - even if it is one of national interest.
Get this formula wrong, and you might end up with a site that may have a lot of registrations or an app with a high download number, but actual usage that lags far behind what is expected. This problem can lead to an almost unnatural amount of user churn, as the population of initial signed up users needs to replaced, not just with new ones to keep growth high, but to backfill those who've stopped using a product. Product success takes more than a good idea, but an entire package - from a clear message of what users get from your product, a fast and smart interface, and near-immediate benefits.
Users don't want to spend a lot of time setting up your application, filling out forms, or hunting for good content. They want to immediately see value, and later tailor it to their specific needs. So don't hassle them by obscuring the app's intent, and hiding the most important, informative or exciting elements behind a nest of menus or a maze of choices. If users are often confused, there's a good chance it's because you made a mistake.
Unsurprisingly, not every application is for everyone. Sites or applications tend to find audiences of similar groups - be it by age, geography, life stage, or any matter of personal preferences. It is a rare event when something crosses the chasm from audience to audience and becomes so mainstream that "everyone" is on it, or "everyone" is using it. That doesn't necessarily mean that by not reaching everyone, the product has failed, but that there is a ceiling on its potential. The company behind the tool then has to make a decision - whether to optimize the product to be an incredible experience for the limited audience, or to modify the product further, potentially at risk of alienating its original users, to attract a wider audience.
You can see this tug of war as initial users of a product (see: The Five Stages of Early Adopter Behavior) can be excited about the prospect of a service reaching the masses, only later to be annoyed at how a service has changed when the mainstream does arrive. It's all too common to see people migrate from community to community online or switch from app to app to keep one step ahead of the pack.
This makes every product decision critical, as well as the ability to listen to user feedback, take rapid action, and act on bugs that impact wide audiences. As I've experienced many times as an early user or as an employee at companies making user-facing software, it's very likely that bugs or quality gaps impacting one person also impact many other people who haven't spoken up yet. Tackling the most reported bugs, even if they are small ones, can be as critical as stopping a short-term outage, depending how forgiving your customers are.
And we as users need to understand that just because we love something doesn't mean everyone will. Other people have different needs, usage patterns and work environments. So while we can embrace the role of an evangelist, what fits us may not fit everyone. I often find, even at home, that my wife's preferences for software and hardware differs from mine. Cast the net wider, and you can see greater diversity in terms of preferred applications, news sources and more. Just because I love something doesn't mean you will, and just because as a developer, you expected me to use a product in a certain way doesn't mean that I will, nor will others. (See: Stop Telling Me How to Use Your Products)
The best product managers I've seen are exceptionally patient and compassionate. They don't bully users into following a strict instruction set, and don't mock you when you come to a different conclusion. They genuinely want to know where they can improve, and learn from you, to ease the onboarding process and make their product even more inviting to the rest of the world. Even if they may be focused on the big picture, every individual user counts, and that makes all difference between success and stagnation.