Extraction yield is not the only metric.
It is fairly trivial to get >=99% extraction yield from your biomass into your solvent, with most solvent systems.
The hard part is getting as much of that as possible into your finished product.
Generally, the higher your desired product purity is, the lower your yield will be.
70% yield to distillate is a pretty standard metric. I know many people who are happy with 60% yield to CBD isolate.
Some people like using cold ethanol.
It is effective, but is not all that efficient from a commercial perspective. At lab scale, that doesn’t matter very much.
Ethanol extraction and post-processing is also pretty well understood, so you should be able to find plenty of useful info about it here.