Open your own website on your phone. Use mobile data, not the office Wi-Fi. Then try to call yourself from it.
How many taps did that take? Did anything shift under your thumb while the page was still loading? Did you wait long enough to glance away?
That's the experience most of your customers get. Not the one on your 27-inch monitor.
Every site I've checked this month failed at least one of those three. All of it fixable, usually quickly.