I’m not sure anyone is arguing that musicians themselves are “modular synthesists” in a restrictive sense.
Nathan Moody for instance: White Box was done with an OP-1. And he just released an album made with electro-acoustic instruments he built himself; it’s gorgeous and creepy, and it still kind of sounds like Nathan Moody while not being anything like his Etudes series.
I feel right at home with modular, but a DAW and VST plugins are fine – I often combine them, and the mindset for one influences how I work with the other.
I think “multi-instrumentalist” is less of a big deal with electronic music than, say, someone who can skillfully play the violin and the trombone and a drum set. It’s less about virtuosity and more about mindset.
They are not necessarily “new” historically – but modular gets one away from the limitations of MIDI (Note on/off messages with a pitch and velocity, which can be modified via CC messages) and piano rolls, and tools that don’t communicate with each other.
Personally: I have worked more with drones, algorithmic composition, and voices with compositional elements that influence other voices far more in modular than I did previously. I often write music without reference to a keyboard, not knowing or caring where on a Western, 12-TET scale my root might fall, tuning intervals by ear and hand. I’m aware of many more sound design possibilities than before; I use a lot more FM, I tie timbre (especially brightness) to dynamics, and the dynamics of one note may be influenced by previous notes. I use fewer voices per recording and almost no polyphony; I make each part speak more for itself… while also knee deep (or occasionally chin-deep) in pools of reverb and delays.
In 13 years of working with VST plugins and another 15 years of synths before that I didn’t find my voice; within about 15 months of getting into Eurorack, I did. I don’t think that’s coincidence.
I feel that Caterina Barbieri’s Patterns of Consciousness, Nathan Moody’s Etudes I: Blue Box, Robert Aiki Aubrey Lowe’s Two Orb Reel, Ann Annie’s Atmospheres, vol. 1 or Gattobus’ Trails would not have happened as they did without modular.
On the other hand, I expect Depeche Mode, Kanye, Coldplay, NIN, Surgeon, Deadmau5, Belief Defect, Venetian Snares, maybe even Richard Devine, might have made similar music with different tools other than Eurorack.