I think both the article and your experience point to the same uncomfortable reality. Degrees do matter, but not in the way they are often discussed.
A degree can provide structure and early exposure to fundamentals, but it does not determine long-term competence. Many people close those gaps later through focused work and deliberate learning.
Most of us are constantly trying to improve one area or another, and feeling behind from time to time is part of the job. If certain gaps are bothering you, you can address them without rewriting your entire past. Picking one area at a time and going deeper than your day job requires can be surprisingly effective, and it often helps rebuild confidence along the way.