There is the mentioned dropping of Postgres support. Postgres is much more popular than MySQL in open source circles, which makes me wonder why go with the latter. Sqlite is still supported, which makes this even more strange. Also, Ghost used to be a single-site publication platform: You would set up a blog with an admin user, and that would be it. Now it's a platform for creating multiple sites, and anyone can do it once you have installed Ghost. The default installer does not ask you a question to turn this off; I couldn't find it in the configuration options, either. The last time I was updating to current version of Ghost, between trying to figure out MySQL and finding out where to customize the site & user options, I gave up.

Thanks for putting the hard work into Ghost, but in the last couple of years, it went from "easy to use self-hosted blogging software" to "publishing platform with highly specific requirements", which is quite a change.