But you can’t make it equally easy to add in every type of functionality. For any type of extensibility design you bake in, some other types of extensibility no

But you can’t make it equally easy to add in every type of functionality. For any type of extensibility design you bake in, some other types of extensibility now become harder. So “making it flexible” hinges entirely on whether or not you can correctly forecast exactly which types of flexibility you’ll need. But this is no easier, and often harder, than predicting how end user requirements might change in the first place!