No one website, app, or piece of software can cater to the infinite number of differences its users may have. You simply can't design everything for everybody. You can, though, look for the common denominators in people and solve for those problems. While a website may have a million users, each with a unique experience on the granular level, you may create just 3 or 4 personas into which most of them would relate in some way. You would do this in order to keep your project user-centered, but out of the weeds and focused on attainable goals.
