Dogshit? No. Different? Definitely. The wild yeasts on the skin weren’t cultivated for alcohol tolerance, so ancient wines would tend to have a lower ABV. They might have some sourness from bacteria found on the skin along with the yeast. Whether or not they’d be sweet or dry would depend on the yeasts and the grapes themselves. There would be a lot of variability from year to year. The Romans, for one, preferred sweeter wines and would add grape syrup, defrutum, made from boiling down grape juice, if the wine was dry. Other cultures might do something similar or just grin and bear it. There was a lot of variety across time and place.

It should be noted that the Romans would sometimes use lead vessels for making defrutum. This would add lead acetate to the syrup, which has a sweet taste, and make it even sweeter.