Then those ideas are very low value.
Great ideas are the ones that make you stop listening/reading and compel action.
Doing is much much more valuable than knowing once there stops being a quiz next week.
Good luck.
If you read more books on the same topic, you still won't remember everything from each individual book, but you'll remember parts of each.
Those bits add up quick, and you'll eventually find that you now know more than you knew before.
If you're in a conversation on something related to what you know you've read before, or you're writing about something related, but you vaguely remember the details you wish to speak about, you can revisit that book and skim it until you find what you were looking for. Now, that part you just found would stick with you for much longer.
All I wrote is about reading books, but it also applies to podcasts.
I too love listening to podcasts and reading books.
I've had threads asking people for their favorite podcasts -
Write them down?
For me, podcasts are for entertainment and exposure to ideas, not for learning that needs to retained. Otherwise it becomes yet another thing that you ruin the enjoyment of by trying to squeeze out the max value from it.
But if you are getting interesting ideas, writing them down to process later seems like a very obvious thing to do.
And when notebooklm came out with their pod cast feature I was in heaven.
I did it with my substack article I did a few days ago on the whole project glasswing. While I wrote it. The damned podcast presented the material in a way that helped explained the topic more than my article did. Its fun.
But +1 to all the commenters (such as parent) who urge (hand-)writing the material (taking notes), active processing, real-world use of the information, and SRS to rehearse retrieval.