Are Kindles / Kindle store that much of a moat anymore? Because now everyone has a good smartphone and can read on that using whatever app. For a niche book I seek out I am happy to install a specific non kindle reader.
If you want to set up your own ebook store it's actually fairly straightforward, at least technically. You just need a normal e-commerce website that sells access to PDF or EPUB files.
The problem is that most people who buy ebooks do not want their collection split across multiple platforms. This is because each platform has their own DRM and app you have to read books in. If you get a new phone and need to redownload your collection, would you rather open up 200 websites to download each author's EPUBs or one app that keeps track of everything you bought?
Yes, I know you can work around this with cloud storage. But that's extra steps; and extra steps add friction and keep people from buying.
Furthermore, this all assumes you're willing to sell your book DRM-free. If you want DRM, or your publisher demands DRM, then you need to ship a mobile app instead of a website with downloads. And that poses a new problem: Apple and Google are not going to distribute your app unless you pay them the same royalties that you'd pay as an indie author on Apple Books or Google Play Books[0]. That's their moat. So if you're trying to create an indie publishing platform, you have to either charge two royalties and screw your authors, or make users jump through hoops to buy books on a website so it appears in an app.
DRM is in fact so much of a trap for authors and publishers that some platforms just outright refuse to distribute DRM-free books; Audible is the worst offender in this regard. Locked-down platforms also trap authors; in fact, the justification that Apple uses[1] for locking down the iPhone is that users can't pirate apps if they aren't savvy enough to get developer creds. Oh, and your special locked reader app is never going to work on Kindle e-readers, because they don't support apps period.
[0] I have no clue if Google even has a bookstore, I'm just assuming this is what it would be called.
[1] To developers, not to the general public, of course
1. Screen is too small. And for everything except reading books "a large phone" is a bad. I've tried big phones. I don't like them. Other use cases either are best served with a phone-sized screen or a laptop.
2. E-ink. I could not imagine reading on non-e-ink. I'd rather buy the physical book, then, and that's a big ask. I'd really have to want to read this particular book.
3. No distractions. Notifications. "Just check my email real quick".