Okay, let's use another example. I waited tables in high school. I was very bad. I knew I was bad, but I worked hard to improve. Still, even after a few years of experience a random person who had never had a job before could walk in and get better tips than me. My boss wouldn't fire me because I showed up for shifts, but I was generally a very poor waiter. Eventually I got smart and stopped waiting tables, and the world became a better place.

It's very possible to be bad at something AND know that you're bad at it AND not be able to reach the proficiency to perform the task at a professional level.

Also, it's pretty clear that I can read. If you are going to insult me, it's better to insult my comprehension or argumentation. However, I would argue that it's generally better to just not insult other people.