Every application developer or UI designer should be forced to sit next to a non-technical person for a couple of hours who uses a slow machine (partly because it's infested by programs and services that they absolutely don't need), while browsing the web or using common applications.
It breaks my heart how much precious time and nerves of these users we're wasting.
They use outdated devices, that still should work perfectly fine, but are grinded down by extremely slow programs.
They don't understand many of the fancy UI patterns _at all_. UI elements without text are the worst offender. Animations and hover effects routinely and reliably get in their way.
They get confused all the time because their UI changes: "I could always click the frobniz here, but now it's gone and everything looks different."
Their system is basically stuck in "dark patterns".
Their internet connections are often relatively slow and unreliable, but common software assume that it's always available going full blast.
To do even basic tasks, they are nudged into registering to this or that, when often a simpler, less invasive solution exists.
They spend ungodly amounts of time navigating stuff, while getting distracted by notifications, misleading information and so on. Often giving up in complete frustration.