Ratings are actually something Netflix has proven to be bad at. They even want(ed) to remove the stars system and replace it for thumbs up. In other words, suggestions, while nice, are not why it became so big.
In the podcasts land most content is free. The shows are usually already containing the category in their title or else in their tags. This means a simple search works very well in opening a series of podcasts in any category. To know if it's any good from your app would be great but again, even netflix sucks at this. Googling for reviews is still your best shot both for series as well as podcasts.
I cannot see yet what Podflix brings over using my Overcast app and simply using the search functionality. I'm already getting all the content I want in a single search and at a great price you cannot hope to beat: free.
So I guess my question is: what problem are you solving? I would have a good session thinking about this and than broadcast very clearly on your landing page what problem you solve that I have today. This can be a problem I don't even know I have right now. However, it is not availability of great podcasts at a great price. I already have that. Overcast also gives me playlist and downloading for a ride.