It's not that trivial to do as an end-user. If I listen to a podcast on Spotify which I'd like to share with you (who doesn't use Spotify), I would have to Google that podcast and try to find a RSS-Link for it, which becomes more and more difficult as most pages now link directly to Spotify or Apple and provide no RSS-url.
Ideal would be an URI like podcast:// which apps could simply register for on OS-level, but I frankly don't know which entity would actually want to drive such a standardization.