But you are expected to find the most optimal solution to a problem, and not just a brute force one. And usually an optimal approach would require advanced knowledge of algorithms and data structures.
I'm not talking about brute force solutions. For many problems, there are things in between <famous algorithm> and brute force. Some problems offer simplifications over more general problems where <famous algorithm> is strictly worse than a simpler, more customized solution (same efficiency, but simpler to write and understand).