"Every game that doesn't allow you to modify the rules is bad, and every game that allows you to modify the rules is good" is an equally ridiculous position.
You've literally given examles of three different games that do not have "Rule Zero". Yet you agree they can be adjusted if the players feel it necessary. The only conclusion we can draw from this is that every game can be changed if the players feel it necessary--and thus there is no such thing as a badly-designed game.
Even if that critical flaw weren't present, it's quite clear that a game can be designed badly separately from whether they permit modification. A game about combat that has zero rules for combat is a badly-made game, objectively, it's literally bad at doing the thing it was designed to do.