It's extremely easy to "beat" the standard library offerings by incorporating what's unique and specific to your situation. They have to be super generic to be in a standard library. Of course, don't re-implement a completely generic list data structure. But implementing a particular kind of dictionary that takes advantage of assumptions that are true for your use case (but not true in general) and is custom tailored to your environment is extremely valuable.
>But implementing a particular kind of dictionary that takes advantage of assumptions that are true for your use case (but not true in general) and is custom tailored to your environment is extremely valuable
This requires way more knowledge than I got from my undergrad classes and in comparison learning that part is trivial forward to the hard part that you can pick up in "refresher" part of a book/article on the topic.
I doubt your average undergrad could do it so I disagree with the extremely easy part as well (heck I doubt they could write a bug free version in the first place, even less a better performing one) that a correctly selected std lib container. Well at least not without researching and testing a bunch at which point the background knowledge is trivial in comparison.
