Non-sparks can replicate spark inventions just not understand them. Otherwise clanks or sophisticated weapons could not be mass-produced, or big projects like Castle Wulfenbach created at all. The same would go with repairing spark technology and this can totally be done by mundane people. Whether non-sparks could ever invent things on the same level given enough time is a different question.
This is a very interesting observation and does fit that early page all too well, since Lucrezia is clearly pointing at Agatha.