I’ve made wine (and a lot of beer). It’s not hard, and people have been doing it for ages, but creating a good, consistent product does rely on chemistry/biology knowledge that they wouldn’t have had back then.

I suspect that a lot of the mystique around wine (like the idea that terroir is magic) is just down to the fact that a few hundred years ago, most wine/beer was trash, and the only stuff we’d consider “good” by modern standards is just down to luck that a batch didn’t get infected with the wrong yeast/bacteria, or exposed to too much oxygen, or a style that is meant to be drunk young (vinho verde) or oxidized (sherry).

There’s probably good reason that much of the wine that was aged/transported long distance a couple hundred years ago was fortified (Madeira, Port, sherry, vermouth, etc.).

Millenia of selective breeding have changed grapes, too. Without knowing for certain, my guess would be that on average, the sugar concentration in the raw grape juice would be roughly the same as now, but relying on wild yeasts or polycultures would not ferment as completely, so the final product would have lower ABV and higher sugar.

In beer, the actual grain and malting technology has greatly changed over time. 150 years ago, German immigrants to America couldn’t brew the lighter styles they were used to because American grain was much higher in protein so they had to dilute it with corn/rice. Older grain had a higher propensity for certain defects, too. Basically you had more inconsistency back in the day, and also just some things that were different.