Saw that one. Lots of good shows to follow up on. Thanks, and I should have done that long ago.
The biggest barriers for me are:
1. Time / relevance and the investment to figure that out. It helps to know the intent of the newsletter too. Some people are adding value to products and services with relevant commentary. That's a good thing, but only when I'm into the product or service. Others are sharing insights and perspective, sort of blogging via newsletter. Like those too.
And I'm search driven, so I'll land on one, and read the relevant bits, and sometimes subscribe. On that note, full content delivered to gmail sometimes is worth it. I've searched my mail, and found very relevant things in there, often long after they were published. Maybe there is something exploitable there.
2. Use of time. I can listen and do lots of things.
3. Interestingly, I would absolutely love a newsletter of news letters, where snippets that are relevant to me are presented in a dead simple mobile friendly read it quick format, or are presented as audio reviews of some sort.
The barrier here is good content that I don't know is good. Selling it to me in an easy to consume form would be kind of like a mentor who presses us to do or read something. Once in a while, I find one, and realize I should have been following it, and then binge on it to get caught up.
I would pay for this one. Having some service, or even persons or person who knows me enough to push and select high relevance things is worth a lot.
4. Speaking more specifically to #1, size matters. Popular ones seem to balloon up, and I'll tune out. To me, a short, but very potent newsletter can be just one item, but it's really worth it. I prefer this to a big one where a few gems are hidden among a lot of other things.