How do I delete these old podcast from my library with Ventura?

Did you click on the ellipsis (…) next to each episode and choose "Unsave Episode"?

I don't have any podcasts but in the Books app when there's a button with three dots (…) right clicking on it gives the option to delete:

Give it a try and see if the Delete option in there.

Frank, if you didn't download them there is nothing to delete to save space. What you are showing is the "Latest Episodes" available for download of that particular podcast.

You're welcome.