Who could really solve these problems, error free, on the spot with no prior exposure to underlying concepts?!?
That doesn't mean all "implement X algorithm questions" are categorically bad.
But put them in a room and say "Make us a 2 layer red velvet cake" with no access to a recipe, and you're not going to get a red velvet cake. It's an easy recipe that most people easily recognize with just a glance, and anyone could make it if they have a recipe on-hand or make red velvet cakes with abnormally high regularity. But most people, even if they're great chefs otherwise, will fail.
Recognizing that a concept exists and implementing a relatively complex concept are different things.
To know how to make a novel cake (not a recipe you've memorized), you need to have a good understanding of how the different ingredients interact. You probably even have a good sense of why they're there.
Those seem like exactly the qualities you'd want to look for in a cake maker. Sure, they'll probably be going from recipes in their day to day job. But they'll be able to tweak them intelligently too.
But, as with a concept like 0, making the cognitive leap to understanding that there should be a way to represent the lack of something is counterintuitive (indeed, consider Tony Hoare's billion dollar mistake. The "right" way to represent the absence of an object is a hard problem). However, once you've been exposed to it, it's not particularly challenging to rederive the necessary pieces.
So yes, complaining about BFS is, imo, akin to complaining about being asked what the result of the arithmetic operation `35 - 12 - 23` is.
I'm not asked to implement BFS every day, but the concept of a tree traversal is incredibly common.
Even more explicitly, a lot of my recent work has been involving automated refactoring tooling, so there's lots of work with abstract syntax trees and control flow graphs, which are trees or graphs, and therefore need be traversed.
Consider that BFS was first published in 1945, while the turing machine was published almost 10 years prior. Is BFS an implicitly more complex concept than a turing machine? That seems like a strange argument to make, but I'm certainly interested.