Each one of us is unique. We all have our own mix of abilities and the challenges that come with them. Some folks might have trouble reading small text and others use screen readers to browse the web.
Many struggle with complicated navigation menus and plenty of us have days when we're just too tired to focus properly.
This idea of a "normal" or "average" user is a myth that needs to die.
When we design websites as if everyone has perfect abilities, we're basically telling a huge chunk of people they don't matter.
Think about it.
Someone might have temporary wrist pain that makes using a mouse difficult. Or they might be trying to read your site while holding a sleeping baby in one arm. Another person might be dealing with anxiety that makes it hard to focus on cluttered pages. Someone else could be using their phone in bright sunlight where contrast matters.
Good design isn't about catering to that perfect, normal user.
There is no perfectly normal person out there. Normal compared to whom?