I haven't looked at the site properly yet, bear that in mind, but to answer your question I probably never have used anything 'interesting' in a couple of decades of working in industry, despite giving a lot of time learning about such things - I do find them interesting.

Nearest I might have got was trying to use a bloom filter in a vehicle tracker, but nope.

What learning about stuff generally has given me is indirect, the ability to dig down and optimise because I understand systems. As I read up on eg. sorting I understand that quicksort is very much not the quickest sort and fixed bad performance bugs from its misuse.

Or understanding Btrees so I can get very good performance out of DBs, even if I've never written a Btree and frankly never want to.

Stuff like that. Maybe one day I'll find the need for dynamic programming and learn it properly, until then it's just a waste of time.

But use them directly, no. Surely sux.