Why does my minestrone soup end up with so little liquid?
Are you "simmering" or "boiling" the soup?

When preparing soup, especially from stock, anything above a very slow simmer is going to reduce the soup, so you end up with something that's more concentrated but - obviously - also much thicker.

What you should be seeing is just a few bubbles escaping to the surface every minute or so.  That's it - that's all it takes to cook.  If you're seeing more bubbles than that, you've got the heat turned up too high and your liquid is evaporating.