How did we even end up in a situation like this?

Capitalism ;)

If donations through Patreon were the only way for artists to get money, I don’t think we would have very many high quality movies, series, albums, paintings or sculptures.

This sounds obvious, because if people don't need to worry about money they can invest more time and effort into their art.

But a. this does not mean it's fair. Not within the art scenes (because a lot of people are working hard but don't have the luck for a breakthrough) and certainly not compared to other jobs.

And b. while a movie like Lord of the Rings or a series like the Sopranos do need a lot of money, many expensive movies are actually rather boring because they have to play it safe in order not to risk a fuckton of money. On the other hand, many great movies had a rather small budget. Avengers: Endgame could have paid for 100x Whiplash or Trainspotting, and I'd rather have more of those. And I think movies/series are the outlier - music is much cheaper to make.

But it's hard to solve or even discuss all this in some lemmy comment ;-)

I feel like it might not be sustainable

The current system however is definitely not sustainable.