Resolution of Effects in Illustrator

Hi everyone,

Sorry I'm still new to Illustrator and still trying to figure it out. I've searched the internet to try and find help but can't find what I'm after.

Basically, I've changed the effect of a solid colour shape to a gradient then added the grain, texture effect, however as you can see the resolution is so bad and I can't figure out how to improve it.

I'm using Ilustrator 2020 on Mac, thanks for any help in advance 🙂