I see tabletop design as an art and not a science
And aircraft design isn't an art? A lot of aircraft designers would probably be surprised by that take! My view is that engineering has elements of both science and art.
In the practice of ttrpg design, as in any art form from musical composition to baking, there are no immutable laws.
It's interesting that you chose baking as an example, in lots of shows I've seen that focus on baking they stress that it's a much more scientific discipline than cooking since there's a lot of chemistry that goes on while baking so recipes matter a lot more.
Things only "work" and "don't work" in relation to a specific individual or a group.
Presumably you're aware that this itself is a definitive statement. Personally I think relativism and treating everything as utterly subjective goes too far. I agree that people shouldn't be jerks about asserting that they have answers they don't really have. But I also think that presupposing that everything is arbitrary entails that game design (or cooking) is not a craft or skill that can be learned or developed, and I disagree with that. Asserting that everything is due to individual differences among people or groups seems to me like jumping to a conclusion.