Podcasting started mostly due to curiosity. People used to discuss topics that were interesting enough to warrant investment into the needed hardware and labouring the entire setup and production. If the topics weren't as interesting, the people were. That is how Joe Rogan begun and built his brand, after all. There was quite a lot of "whoah" factor back in the early days.

I do not think this has gone away. Yes, market saturation waters everything down to the common denominator. Podcasting is no different than any other commercial or public market. But there will be always outliers. The only difference is that back in the old days(early 2000s and 2010s), your choices were limited, which made it easier to pick. Today, you have to invest time and effort and hunt down those good podcasts that match your interests by sifting through a ton of the noise(badam, tssss).

I was big into podcasts, even started my own. Until I realised that without interesting guests to bring in week after week, there is no point in it.

But I think that the main issue is, and has been for a very ling time, that there is really not a single good user interface for consuming podcasts, especially offline, managing podcasts or discovering new ones, keeping tabs on what is going on with individual shows or even getting recommendations on and being able to purchase your own podcasting kit, so that you don't have to research and learn about audio, video and other related things that might detract someone from thinking about starting their own podcast. And also all of this in packaging suitable for different consumption situations - walking, driving a car, riding a bus, being at work or at home. Yes, there were many various apps and websites, but they all suck and lack in any useful feature. They essentially just aggregate podcasts and offer RSS feeds. That's kindergarten bs.

There's your $1B idea.