Well, I'm guessing I have two podcasts in there, one of which is completely inactive and the other of which I haven't published anything new to for well over a year. There are a lot of podcasts out there that are pretty inactive and some were only intended as being limited series in the first place. So, yeah, if the universe of discoverable podcasts is 4 million it wouldn't surprise me at all if an order of magnitude fewer are creating new content. (Though older content, e.g. for The Big Dig limited series can still be historically noteworthy.)

Podcasts should be thought of as limited runs, not like never ending radio programs. That's just the reality, regardless of the original intentions.

I think the move to announced seasons is a good middle ground. It tempers expectations and gives creators a break or stopping point.

There are definitely podcasts that are of historical interest. I mentioned the big dig one. My former company also did some computer-related podcasts that are sort of evergreen, e.g. related to Soul of a New Machine. There are also ones related to speculation about some current TV show that mostly have a pretty short shelf life.

But agree generally. I think if I were to undertake a new podcast, I'd probably use seasons. Gives a good point to decide, nah, I'm done with this topic. Otherwise, the natural path is to just peter out.

I'm not sure how you solve discoverability other than personal recommendation from someone with similar interests. As noted, there are a ton of podcasts out there and many won't overlap with your interests, others are largely or wholly inactive, others are poorly produced, etc. The fix, such as it is, is probably to have a podcast reviewer who isn't in it for payola, who overlaps with your interests and sensibilities who makes recommendations on a blog.