Harper May interview questions

I had 1 interview that went well over the amount of time scheduled. the questions were the kind of questions you would expect and then we also got talking about more general things including the history of the company. I was given the impression the conversation went really well. Was given feedback a week later (via the rec2rec agency) that was vague and not a "real" reason for rejecting a candidate- they believed I "would not find the role challenging enough". There were many red flags prior to the interview, in particular the reviews from their former employees, so I do not mind being rejected by this company. I went in with a completely open mind, but when it comes down to it, being given a vague piece of feedback with no real reason for a rejection or thanks for the time spent on the process is not something you would experience when interviewing in a highly favourable environment.