In the video in the post I just boosted, @anildash says #Substack is now boiling the frog in a slow move from email towards lock-in. And of course they work with Nazis etc.
What we need is an effort between newsletter publishers like #Ghost #WordPress etc and reader apps like @wallabag to build an ecosystem like podcasting. To make it smooth while remaining totally open. I'd argue for using #ActivityPub in addition to RSS to support boosts. Then we need decentralized money.