I'm really excited about window.showDirectoryPicker and the local-first web apps it will enable. There's lots of talk about local-first sync engines, but the best sync engine is one you don't even manage, like the user's file system / cloud storage service!
Yes, I think this modern trend towards storing user data in app/website-specific databases instead of in files has been bad for consumer freedom. Files are naturally portable and provide a interface for inter-operating with competing software in a way that data stored in the cloud or an app-specific database does not.
APIs that encourage websites to store user data in files are a positive thing.