MVST. Full Stack Developer interview questions

First an interview with HR, then they send you a challenge to do at home, which is not complicated but very long. I have a 8h a day job, so I spent another 8 hours over 2 and a half days to finish the challenge, about 20 hours. The test consisted of making the backend of a store, and layout everything in the frontend together with responsive. I detailed everything I did, the why, the things I would have done later, and I attached screenshots and videos. So, I had an interview with two developers, which felt like a 1 hour quiz about devops, backend and frontend. They seem to like the test and my skills put into it, but later I got a generic email that I didn't pass the test. Thanks to my headhunter, it seems that I "didn't demonstrate deep knowledge of devops (even though it wasn't required) and that I "didn't explain the questions in detail" when advised not to explain too much and get to the point. It feels like a waste of time, in my opinion, I think it's a mistake to have two programmers and not managers who say if a candidate passes the phase or not.