I must say the AR-15 is probably one of the most ergonomically intuitive rifles. Its hard to improve on the controls or manual of arms of this guns. Except for the bolt release. Its fiddly to lock the bolt open on the AR, and while whacking the ping-pong-paddle with your palm works like a charm to dropping the bolt, its not a positive action like pressing the mag release or flicking the safety lever.
I’ve shot several rifles with a BAD lever, and when I get an AR, it is a MUST have!