Amazon Software Development Engineer II (L5) interview questions

One of the most negative interview experiences in my entire career. Had applied through a consultancy. The complete process took almost 2 months with only me following up and no feedback from them. Completely unprofessional and not expected from the likes of Amazon. The process started with an online test which I could clear easily. Following with 3 f2f rounds in their office. 2 coding and 1 design did decently. The feedback for this round took almost a month and then they scheduled 2 more rounds. 1 coding and 1 Hm round. Did well again. But they seem to just reject people for the sake of it. Got feedback from the consultancy stating design and coding skills weren't to the mark. I am ok with it but then why to schedule un-necessary rounds for it and keep a candidate waiting. Also there was no design based discussion in my 2nd Hm round, not sure form where they get feedbacks when I wasn't even evaluated on that. Just made me wonder how would people be actually working there when their hiring it self seems out of place.