You wrote that people dislike 'hard' rules because they can't understand them
Actually what I said was:
And I think we can agree that some people find 'hard' rules inhibit their suspension of disbelief because they can't grasp the mechanics.
Some people. Not all. ie not all those who dislike hard rules do so because they cannot grasp them. Also hard rules need not be overly mathematical, they might just require lots of memorisation.
There's a reason you don't find a mosh pit at a folk music festival, why organizational psychologists spend countless hours researching the best way to do brainstorming, why there are rules in improv theater, why a charismatic church creates a different kind of environment than a liturgical one, and why math-heavy game systems are counter to roleplaying. It's all a matter of which parts of the brain you are focusing on. This principle (called 'structuralism') has been recognized by social scientists at least since Malinowski. But you are, of course, free to ignore it.
It's interesting that you take this tack because some people enjoy mosh pits and others folk festivals (some might enjoy both at different times). Are you saying that one promotes the enjoyment of music and the other does not? Or that the environment in an evangelical church promotes spirituality more than that found in a liturgical one? They're unrelated to why a maths heavy game
might run counter to roleplaying.
But your definition of maths heavy interests me strangely. Tell me something that's maths heavy about 4th ed D&D. More maths heavy than found in 3.5 games. There's a powerful amount of pesky adding and subtracting done in 3.5: synergy bonuses, situational modifiers, shield bonus, superior weapon, defensive boost for a set spear versus a charge etc. And game theory... 3.5 is full of it. whole supplements have been devoted to maximising the abilities of character classes and the multiplicity of feats and their possible combinations mean that exploring every option is a fairly complex task.