I would say important part of podcasts is delivery process. Which at this point due to wide spread of on demand streaming services has somewhat lost many of it's unique features.

Some years ago if someone said a talk show I would think TV or radio which might be prerecorded but was still broadcasted at specific time.

Not all podcasts are talk shows. Some podcasts have more of news update format, they are still called podcasts due to technical format, but you wouldn't call them talk shows. There are also more educational podcasts, with single person informing people about some topic that isn't news.

When podcasts started a distinguishing feature was that you would download them (at time of your chose) and later play them at time of your choice. Another factor is since it isn't radio or TV, medium was a lot more accessible to many creators. This allows creation of much wider variety of shows for niche interests compared to what you would get on TV or radio.

Now that a lot of media is consumed on demand through various streaming services like Youtube, Netflix, Spotify but TV and Radio usage has significantly decreased that's not unique anymore. Even traditional media companies might be publishing parts of their shows either on their own or existing platforms after the initial broadcast, thus allowing on demand access to their content.

One more change that has reduced podcast standout features is overall internet speed access. Internet largely has become fast enough that directly streaming audio is easy, there is little need to predownload it. Not only it has become fast, through the mobile networks it's accessible on the go. For a long while even if internet speed was fast enough for audio streaming, mobile internet was quite expensive thus encouraging to download stuff at home for later listening on the go.

On the topic ease of creation. While there might some podcasts which are now quite popular and the budget that exceeds smaller talk shows on TV and many on radio, the lower bound for podcasts is still much lower. TV and radio has limited broadcast time available, so there will always be some lower bound of budget (depending on size of TV channel) which will likely be above most podcasts (in terms of amount published, not necessary amount of listeners).

Limited broadcast time has another interesting implication - limits on length. You will unlikely see talk show on TV that's much longer than an 1.5 hours, and anything shorter than 15min will likely be part of bigger show. Podcasts can be as short as 5 minutes (usually for news update style podcasts) and up to 2.5h or longer. Even a single podcast can significantly vary in length between episodes depending on guest, you can't do that on TV or radio where you have specific time slot.

Names aren't always about content but often also various technical details and loosely defined common properties. Why do we need separate words for CD, vinyl record or Radio, for saying "I was listening a CD", when we could just say listening a song regardless of how it happens. Having more words allows expressing more information. An when you say that you listened a vinyl record that implies a lot more than listening a song.