You’re quite right... there are actually no such things as systems or structures — they are merely generalisations from accumulated instances in the flow of discourse.
Blogger Comments:
[1] To be clear, in this context, systems and structures are abstract things that serve as participants in clauses in the field of linguistic theory.
[2] To be clear, systems and structures are abstractions in the metalanguages that theorise languages.
∞
Postscript: McGillicuddy promptly denied that he held the view ascribed to him by Rose.