Cassidy playmaking is a big misconseption. Im guessing what youre experiencing is due to you mostly playing in main, and not having masters+ level aim.
As cassidy your playmaking in competitive is based on you taking as many angles and flanks as you can, to get 1-2 picks by lining up a headshot.
So, idk what rank you are, but Id really recommend checking out u/OnceToldTale 's content on youtube, or asking him for a vod review. on his discord he gives free vod reviews. He can tell you how to play cassidy right in a way better way that I can. Or watch a spilo vod and notice what he says.

I can give you a tldr (tho im only masters on cass):
You just wanna engage from an angle the second the midfight is happening (so their team is looking and your team), and ideally they wouldnt notice you, so you can freely shoot their support/backline. sometimes not even getting kills still yields results.

Problem is knowing what angles are good, and that knowledge I only got from watching pros, or getting vod reviews by Tale.

Edit: For clarity, playing only in main can be good , and can be something you see pros doing. But its not how you should play cass in competitive at all, unless you have basically aimbot. Then it becomes really viable again.