Old, mediocre league player having a frustrating time trying to come back to the game

I was never a great or even a good player, but I wasn't too bad. Mid tier Silver was the rank at which I left the game (if memory serves, I did technically push up into Gold V just before calling it quits, but it was very much luck of the draw & I don't consider myself anything beyond Silver).

I am now pure garbage. Just absolute trash. I am trying to get back into the hang of things, and not having success, and it is going so badly that I am not having any fun at all. :(

I understand all of the fundamentals of the game (the importance of map control, last hitting, using minion aggro advantage in a lane, etc)... and it doesn't seem to matter. Often what happens is I'll get into a lane with a Zed or Talon or Yasuo, and they will just zone me right out of CS. If I try to use minion aggro to win trades... I just don't. They out-trade me, and at 6 they all-in me and often kill me.

Katarina's rework seems more or less like it has broken the character (...dunno why there was apparently the need to destroy someone who was never a great pick even in her limited heyday, but whatever), and that's who I played most games with. Now I don't know what I'm supposed to do. Buy Zed and/or Talon? I don't really like them, though. :(

I'm just at loss as to where to even begin trying to improve, so that this feels more like entertainment and less like torture.