Television

I think one thing you have to keep in mind is that a lot of leading contemporary actors who get cast in modern TV series are not down to do 20-24 episodes a season as leads. Many of them are on other shows, or films and don't want such an obscene filming schedule - and are able to negotiate that as an outcome. Apart from which, a contemporary 20-24 episodes long TV series really has to compete in a way it didn't 20, even 10 years ago. Unless you're just a by-the-books network medical/cop procedural with a built-in presumably older audience, there's a lot more competition for people's attention now.

When TV shows were airing in the 90s and early 00s and late 00s, people weren't really watching korean TV, or nordic noir for instance. There was very little of it comparatively, and what there was barely made it to the USA. This means getting people's attention for a TV show with such a large amount of episodes compared to everything else is a pretty tall order. Audiences also expect, I think, better budgets per episode now.

I watched Mr. Robot years ago now, but I'd disagree that it was harmed by its episode count. It was intensely serialised and packed a lot in it, whereas the majority of older 20-24 episode shows were primarily 'monster-of-the-week' with some of them having over half of their episodes a season completely self-contained.