You're assuming these walled gardens are going to work. I, like you, use Overcast. There is nothing on any of these platforms that would inspire me to pay for them. Some of the celebrity “exclusive” shows I believe rely too heavily on their name and not enough on actual content that I want to listen to.

While I see your point that if everyone makes walled gardens the joy of listening in one place may go away. On the last episode of the Podcasters Roundtable, Ray Ortega made a great point on how many of these “exclusive” shows are no “Exclusive” on season two.