I have a feeling you are selling yourself short (and being overly hard on yourself, something I'm well acquainted with but more easily recognize in others).
Based on your technical focus, you're clearly (in my opinion) way above the "average" developer in technical ambition and appreciation for computer science.
A bit of unsolicited advice: If you organize your preparations around the concept of providing value to a prospective employer, rather than merely getting hired to write code, then I bet your outlook will change. One book (and definitely not the only one) that can help with that is Bob Martin's The Clean Coder: A Code of Conduct for Professional Programmers:
Based on your technical focus, you're clearly (in my opinion) way above the "average" developer in technical ambition and appreciation for computer science.
A bit of unsolicited advice: If you organize your preparations around the concept of providing value to a prospective employer, rather than merely getting hired to write code, then I bet your outlook will change. One book (and definitely not the only one) that can help with that is Bob Martin's The Clean Coder: A Code of Conduct for Professional Programmers:
https://www.amazon.com/Clean-Coder-Conduct-Professional-Prog...