It's completely relevant. If you just want the pitcher to hit a target, that's cricket, not baseball. The oval shaped strike zone called by umpires substitutes less hittable pitches in the corners for more hittable pitches over the plate. They're mentally substituting the "rule book strike zone" with "was the pitch hittable".
The other problem your proposed rule has is it makes major league baseball a very different game than amateur baseball. Amateur baseball will never have an automated strike zone and will have to continue with the rule as written today. It will be even more difficult to figure out which 16 year old from Venezuela will be the best hitter in the majors. It also is a huge break with the past - players who are currently all-stars with huge contracts would become overnight washouts.
If they make the strike zone a fixed zone I probably stop watching major league baseball.