Well it’s all you. You kept at it and didn’t give up.
And yes, streamers make a difference.
The Canare 4s11 speaker cables aren’t terrible. I own a pair. They’re not resolution champs but they also don’t sound harsh.
Work on room acoustics next. Treating first reflection point (side walls) usually does wonders to tame harshness. Bass traps behind speakers help as well - the bass is more focused and controlled which will help balance out the mids and highs and with better bass the sound will be fuller and not as brittle.
Once you’re done with room acoustics I strongly recommend Acoustic Zen Satori over Zavfino. I owned pretty much all AZ cables and I can tell you they sound natural, don’t have the sibilance in vocals and have excellent details and warmth. On a used market they’re a bargain.
Zavfino is just OK. I tried their interconnects and they were mediocre at best. A friend of mine had their speaker cables and didn’t like them.
Don’t get too hung up on OCC. it isn’t a guarantee of perfect sound. Keep the neotech when it arrives but focus on good room then speaker cables.