I think spacemanmatt might be implying that working in IT has a tendency to make one feel stupid. ("The more you know about IT, the more you realise you don't know about IT.")

This isn't unique to IT. There are many fields where there are always new things to learn. However, a career in (say) selling cars or owning a restaurant would require much less lifetime learning.

There are ways to improve how smart you are - it is largely a learned & practiced skill in fact. One could potentially become much smarter by working in another domain as opposed to spending the same time in a different one. There are always opportunity costs in the choices we make.