Funnily enough even the tightest drafted legalese is actually often subject to a range of ambiguity and loopholes. I feel it can be a quality inherent in certain language regardless of whether it's plain English or legalese, particularly if there is money at stake in injecting a degree of ambiguity into the language (which is what I'm paid to do!).

Overall, if done correctly there should be no issue with expressing the parties' intentions in plain English rather than using dense legalese. It's something I strive to do every day in my job for sure.

Of course I agree with your general point about laws being drafted to be precise and narrow, it's just that using legalese doesn't always secure this objective. Sometimes it's just clear that the draftsperson was having a bad day.