There are literally dozens of different kinds of basil. Soil has quite a lot to do with its quality. Not just the basic NPK, but minerals (calcium, iron, zinc, magnesium, etc.) and minors. I get my soil tested every year and always find it to be low in nitrogen. Two years ago it need a lot of iron, and this year some potash (green sand) as well as a bit of gypsom. Gypsom will help to break up clay soils too. Also soil pH needs to be suitable for most herbs and vegetables. Genovese basil seems to wor well

Here is a link that might be useful: Pesto basil- Superbo

The first year after buying our house I found that many of the existing vegetable beds yielded pretty bitter tasting stuff - beets that were so bitter they were inedible, stunted & bitter green peppers, etc. I determined I had two problems - a very hot & dry summer that combined with utterly spent soil to give me a 'bitter harvest.'

The previous owners had used only chemical fertilizers on the beds. No compost or other organic material. Just mostly spent heavy clay and the earthworm count was about nil.

We've spent years adding compost from the household bins and have bought soil, manure, etc. to add to the beds. It's still a work in process but most veggies fare very well. Just loosening the soil by adding organic matter will make your gardens a lot better for you. It will also add nutrients. But getting your soil tested is a good idea. It will show if there are specific problems to be dealt with.

FataMorgana