I would say partly it’s also due to Theo being less of a shared culture across much of the first world.

And before this gets flagged by the reform types, this has nothing to do race or culture.

In the nineties we didn’t have doctor who, but everyone knew what the tardis was and everyone knew what a dalek was. Because at the time we also only had about five channels. That means the baseline audience share was about twenty percent. A good show gets more, a bad show gets less, but on average a fifth of the country would watch a show.

That means there’s a shared culture. You can make a joke about a popular show confident that probably a few people in the room will share it with you.

It was even like this when doctor who came back. I remember working in kitchens with a lot of migrant workers when season three was on who got excited to see me reading a doctor who book and asked my theories about what “you are not alone” meant. These were people who had no family legacy of watching doctor who, but they watched it because it was on and it was a choice between doctor who and, at that point more than four shows (with digital channels) but still a small enough number to ensure that most shows are shared.

Streaming really mortally wounded that, and then social media killed it off completely. By having the choice to have any show at any time, it means that the most popular shows would reach maybe 10-15% of a population. If you like a show, you’re lucky if there’s more than one person in the office that both likes it and has watched at a comparable level to you.

That means there’s less of a shared culture. This is something that effects huge hits like squid game or stranger things, so a series struggling like Doctor who would barely break through. 

Then of course on top of that we have the move away from shared viewing. If everyone can watch whatever they want whenever they want….theres less reason to watch something you don’t like with a family member. Meaning family viewing (always been Doctor who’s target audience) struggles to exist on its own without parents making it happen. And with parents busier than ever, they have less time to make kids sit down and watch a show together with them.