In an attempt to decrease the maintenance burden, and because the new abstraction and APIs in Slate's core packages make things much easier, the total number of packages has been reduced. Things like slate-plain-serializer, slate-base64-serializer, etc. have been removed and can be implemented in userland easily if needed. Even the slate-html-deserializer can now be implemented in userland (in ~10 LOC leveraging slate-hyperscript). And internal packages like slate-dev-environment, slate-dev-test-utils, etc. are no longer exposed because they are implementation details.