Home cooking varies so much, and so do people’s tastes. So there’s no way to solidly measure this. Everyone’s experiences will be different in ways atop ways.
My own tastes applied to my ready memories of my own experiences, let’s see, the raw data looks something like:
So-so
Ok
Great
So-so but became very good
Great
Great
OMG WTF is that? Yuck!
Good
Good
Not Good
Not Good
Good
Good
Good
Very Good
Good
Good
Good
Good
So my experience has been mostly good or very good (around 60%) another over 10% great, a bit over 15% Ok or So-so, and about 17% not good or worse.
Pretty good odds, and a good chance of getting very good or great food – almost certain, if you go back to those people, and avoid the others.
The demographic pattern I seem to notice is, for my own tastes and experiences anyway, that rural American home cooking had the highest chances of being bad. I think cities in the US tend to have much more exposure to good food (especially restaurants in Seattle, San Francisco, Portland), while people in rural areas often haven’t been exposed to as many types or ranges of quality – although if they’re using fresh local ingredients, that can be amazingly good.