Idly occurs to me that Substack, Shopify and Amazon are all points in the same problem...
A small, curated store is easy to browse, but how do you know the store exists?
But once the store is big enough that everyone knows it exists, it's too big to browse.

Shopify has hundreds of thousands of stores. Each store is easy to browse, but how would find the right store?
Amazon is one giant store, but you can't browse at all
And once Substack has 100k writers, you won't be able to browse it either.

Shopify could try to make an interest graph and suggest new stores. Pinterest does some of this, and Instagram is building it. Medium tries to suggest stories, and Amazon suggests products. And Substack says it doesn't want to.

But if Substack doesn't built a network - an algorithm - it can't get me readers, and it's a tool - Mailchimp with less control and a slick Stripe integration

Once you get any kind of scale, the only way that a tool can give traffic/audience/exposure to its content is with an algorithm: search is down-funnel and browsing doesn't scale. Or, or course, the content creators advertise, either on-platform (Amazon, SEM) or elsewhere

All search grows until you need curation, and all curation grows until you need search.

To put this another way, these remain two of the more important questions in a 20 trillion dollar industry https://twitter.com/ggreenwald/status/726379399147327488