I had a replay review, and yes it helped quite a bit actually. I learned that I like to take bad trades in large minion waves (I tunnel on harassing my opponent), and that I need to stop trying to rush things when I spot a kill opportunity, because I get impatient and end up making a mistake that turns a good situation into a terrible one. I learned that I rely too heavily on my experience playing Katarina, and end up playing on autopilot and not thinking strategically about the game, the champions in it, how their kits interact with one another, and what my win conditions are.
It can be hard to spot these things on your own, unless you know what to look for. I'd highly recommend coaching if you truly want to improve at the game.