Yes that’s because the sugar gets converted to alcohol by the yeast and the more sugar the grapes have the stronger the wine will be. Doesnt mean wines are gonna be really sweet.
I prefer dry red wines, cabernet sauvignon is actually my favourite, but I still prefer not to drink.
Grape juice, like I said, is a poor juice to begin with. But, it has a lot of sugar, which comes in handy for the application I described. The final step in the process is usually evaporation, which concentrates the sugar solution somewhat.