Target Designer interview questions

I was contacted by a recruiter for a design position. I have a good 10+ years in this industry and in the specific field they were recruiting for. I saw a few red flags and in all honesty I should have halted the process when they asked for a test project. Giving that my experience is 1:1 what they were seeking, I should have refused the test project, but of course this would have ended the interview process. I had a series of interviews over the next couple of weeks which went ok. In the end the reason I was giving to not receiving an offer was "we decided to go in another direction". This is the most generic response you can give, and I expected more. I asked for more feedback but was given "sorry we legally are not allowed to do so". So now I will never know if they did not like my test project, or if my personality didn't jive with their team, or if i was too opinionated for them because they refused to give any sort of feedback which is a major cop out. I wasted over 30 hours on the test project and interviews. It's my fault for not seeing the red flags right away, but hey you live and learn.