I use category theory quite frequently when doing functional programming. Unfortunately it is not taught in CS programs AFAIK. I rarely implement any tree kind of algorithms other than a simple tree visitor.

An understanding of time/space complexity (Big O Notation) is also relevant to evaluating approaches. A senior level developer will use this to make high level choices.

I also use compiler theory when writing parsers and simple DSL languages.

Honestly, never really had to deal much with red-black trees or linked list algorithms.