If you consider yourself an “average programmer at best” why are you applying for high-flying startup engineering jobs? You don’t have to know or care how to write a BFS graph traversal on the spot, but if that’s the case, the problem for you isn’t really a technical one, it’s a social one. You’re not going to be a good culture fit for those teams who do value that.

Stating so emphatically that questions about foundational data structures and algorithms have “absolutely no relevance to the vast majority of open software engineering positions” doesn’t communicate what you think it does. You’re focusing on the “data structures and algorithms” part, but it’s the “claiming you know what is and isn’t relevant for the vast majority of software engineering positions” that is the real issue here.

Join a small web/app development agency who will support you doing great work delivering big results for clients who will appreciate your skills much more.