Wave management got kind of bonkers after last minion changes. It works fine up to a point, and then it does not - or at least not how you expect/were used to.

If the wave is trapped in the enemy side, you got to go there and make it hit the turret - otherwise it won't be bouncing anytime soon if left unattended.

Either prepare a lot of vision around and go there quickly, or use that time where you don't have access to it to do/force something instead. You got to commit a bit more now or play champs that can "cheat" their way out of it somehow (i.e quinn or kai sa farming and subsequently joining back with R to their team much quicker than the enemy can respond).

This wasn't worded the best and my examples may suck/ be a tad inaccurate, but i too noticed my cs decreasing a lot recently and went to find why. I mainly abused wave management prior recent patches to reach high cs and still be present in fights, and suddenly i wasn't managing to do it anymore.