"Illusory superiority" refers to the tendency of people to overestimate their own abilities, skills, or qualities compared to others. Essentially, it means thinking that you are better than you actually are. Full definition
Alfonse here is suffering from the «Dunning — Kruger» effect which is a cognitive bias in which unskilled individuals suffer from illusory superiority, mistakenly rating their ability much higher than is accurate. (religion.blogs.cnn.com)
Indie authors are «unskilled individuals that suffer from illusory superiority, mistakenly rating their ability much higher than is accurate. (goodereader.com)
It's a cognitive bias psychologists call «illusory superiority.» (canadianbusiness.com)