Deloitte Senior Software Engineer interview questions

first i went through a jam session and next for a TR round which was very basic and then an another Tr round which was based on some qsns regarding projects and then HR but unfortunately i got rejected in HR

Initially, I had to complete a coding challenge via Codility (similar to HackerRank). I did well enough on that to be asked to complete a second coding assignment. With the second assignment, you are sent some code via email (zip file) and have to make improvements as well as implement some additional functionality. I had 24 hrs to send it back. After having completed that assignment, I was invited to participate in a technical interview where we would discuss my second assignment. After all of this, I was told that my core Java skills were lacking. After passing each coding challenge/assignment? I feel like I completely wasted my time.