There were 4 rounds which took place every consecutive day which was great but the HR was quite unprofessional. She never responds to the emails and changed the scheduled interview timings without informing after having discussed the same on the call. I had to call her to ask why a certain person wasn't available for the meeting only to know it had been rescheduled. She included links to multiple meetings in the email some of which I wasn't even supposed to attend which created a lot of confusion. She told me she'll get back to me by Monday regarding the outcome of the interview but didn't. I had to call her on Tuesday morning to know I had been rejected because my platform round didn't go well which I think isn't true at all, maybe you want a candidate who knows 100% of the questions asked and answers each one like a robot without fumbling.
Either way, I don't mind a rejection for whatever reason however, it's professional courtesy for an HR to get back to the candidate so he can have closure and move on. You seem to stay in constant touch with the candidate while he's interviewing but ghost him later on. I might probably expect this from a startup but you're a well established company.