A replay system will DRASTICALLY improve my and many of your gameplays and see what mistakes you made in your matches and what could have been done.

But as for my opinion , in order to improve i should compete against tougher opponents, which means smurfs in my rank games. Now its tough to get what they are doing if you are constantly getting killed without knowing the reason how.If there is a replay system i can see the immortal's perspective and improve. The angles they hold, The tricks they use, Agents abilities they utilize etc.

The higher you rank up, the harder it is to find new things to learn and thus it is harder to improve. A replay system will definitely help alot to find those new things to learn.

Also if you can share the replay file just like you can in CS or old COD games, it would be even better to give your replay file to a professional and they teach you how to play and fix your wrongs.