It's wise to keep in mind that not every recipe is a good
one. Some are designed with far more care than others.
It could be that your pizza recipe is simply calling for
too much flour. Or perhaps you're working in too much
flour as you knead the dough.
Usually recipes that call for yeast suggest a range in
the amount of flour, for example, 2.5 to 3 cups, 6 to
7 cups, etc., because the moisture content in flour varies
depending on how long the flour has been packaged and
the humidity of your kitchen. Humidity makes a surprising
difference to how much flour you will need to create the
perfect crust (or any yeast bread for that matter). You
might even find that you need more flour on a rainy day
than on a day when it's dry and sunny. Getting to know
the "feel" of the dough is as important as being flexible
in slightly varying the amounts of the ingredients.
If your recipe gives a range for the amount of flour,
begin by adding the smaller amount. If it doesn't, begin
by adding less than the recipe suggests. Then, as you
knead the dough, add just enough flour so the dough isn't
sticky. Mixing dough too long will develop the gluten
in the flour to make a stronger crust, but it shouldn't
have much effect on dryness.
You could also try adding 2 tablespoons (25 mL) of olive
oil per 3 cups of flour. The addition of oil makes a softer
pizza crust and adds to the tenderness of the dough.