I am surprised some of the big ones haven’t been mentioned yet -
Radiolab - Not really sure how to describe this podcast. It’s superb journalism at its core. They do both short and multi-episode long form about a variety of topics from science to history to current events. For example, how dinosaurs died when the asteroid hit earth, the story of a Guantanamo convict with the same name as the host, and how poorly computer databases are designed for names that are outside the norm.
Planet Money - An excellent economics podcast where complex topics are distilled in fairly short episodes. They recently released a completely AI generated episode which was incredibly scary with how good it was.
Serial - One multi-episode series at a time about complicated criminal cases.
What Roman Mars can Learn about Con Law - Started off during the Trump Presidency when tough questions about the US constitution are being asked given his penchant for pushing the legal boundaries and norms.