Since I vehemently despise ads I have no issues with the subscription model as long as it remains convenient to play the audio any way I feel like (i.e. no intrusive DRM).
So I actually think that's a good evolution overall, I wish more of the internet moved away from ads and towards other monetization models.
For your audio app I suppose that it'll mean that you'll have to strike a deal with the podcast platforms to share some of the revenue or figure out an API to let people use their license keys on third party players. I understand that it's annoying but that sounds perfectly fair to me.