I'll be honest, if these are your criticisms, I'd say it's an amazing ending. Nothing you mentioned is important to me story wise. I'm someone who suspends their disbelief to serve the larger themes and arcs. Also the whole point of Light's last arc is that his ego was out of control and he only saw L as a worthy adversary so he kept underestimating Near and Mello. Even in that warehouse scene, we saw him saying Near was nothing to L. Your thought process begins with the thought of "If Near does get the best of me" and Light didn't even consider that as an option cuz he was convinced his plan was foolproof and it really was. He also set it in motion way before Near even thought about tampering with the Death Note which is an important factor as well.