What you're describing is know as the Dunning-Kruger effect explained in Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lea

What you're describing is know as the Dunning-Kruger effect explained in Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments (1999).