Mozart was talking about patronage, not rent seeking via artificial scarcity.

so far as I can tell, Mozart never said it. I was quoting my music history teacher (who, admittedly, may have been paraphrasing from some of Mozart's private correspondance, or a Mozart scholar). Also, Mozart was unique in that he was one of the first composers to strike out on his own and NOT have a single specific patron. Unlike Haydn or J.C. Bach - both of whom taught him - he was not a servant of a court. He had private patrons, yes, but they're more comparable to Patreon than they are to other actual Patrons of the time. For example, Mozart owned his music - the Esterhazy estate owned (and still does own) Haydn's music.

I have no sympathy for the industries that gave us DRM and the DMCA.

I understand you're talking about broader reach of media companies, but I'm mostly talking about professionals in the industry, not companies. There is no "Big Nature Photography" like there is "Big Record Companies" - Unless you count National Geographic, maybe? Getty Images, I guess, but they're usually more about photos of people.

Hotlinking has been considered rude since forever,

we hotlink here all the time. Granted, we are MUCH smaller than reddit. However, this is not even really the point, the point is that often the people posting won't even cite the artist - they're not even giving due credit.