I would like to think there is still some secret mojo to speaker building
I think there is, to an extent. In general the game is to correctly navigate the innumerable trade-offs so that you get the most pleasant sound you can, within whatever constraints you have. Generally, this means aiming for flat FR, even dispersion, low distortion. But unless you have unlimited budget and no size constraints, you have to make decisions on how to prioritize those and what sounds better to your ear. How does it sound when you move the crossover 500hz lower to benefit directivity but at the expense of distortion? How wide to make the baffle, where one direction benefits low frequencies and the other high? Etc etc.
