Legalese is a cost-reduction technique founded on the principle of making your potential future case look as much like a previous case, even word for word, as possible.
Legalese features complex grammar, anyone with good English skills and a lot of time could rewrite most laws so they are much easier to understand without losing all the cost reduction legalese provides.
Surely, your claim would only apply to contracts or court decisions, but not to laws.
Hm, interesting thesis. You should post that as a toplevel comment.