I would challenge what you’re saying. An integrated synthesizer like the Model D doesn’t make the normalled signal path apparent. On the other hand, modular forces you to see exactly what’s happening. You wire an oscillator to a filter. You wire the filter to the VCA. You trigger the VCA with a voltage envelope. You need a good teacher or tutorial, but if you have that, modular or virtual modular is a far better teaching tool IMO.