Have I been drinking old wine this whole time?

Many times when I’ve had cheap wine, it had a really bad after taste. There used to be an old saying that expired or old wine would taste like vinegar.

And there have been many times a wine I drank tasted very bitter and sour.

But occasionally when I spend a bit more, or get wine from a good restaurant, the wine tastes perfect: silky and smooth and fruity or earthy etc.

Wine isn’t supposed to taste bitter and sour, right?