Having had a number of bad colds before I actually got a bad flu, I always thought my colds were the flu. Not a huge deal. When it was confirmed to be the flu when I talked to her later, the mobile doctor said that many people think the same because they tupically don't go to the doctor for confirmation, if the doctor even chooses to test.
A real (non-covid) flu had me feeling like I was on death's door for a week, and much of that time was spent wishing it would take me.