Obsidian is plain Markdown and JSON files.

There can't be a will from the devs to make it hard to sync.

It's just that unlike git or Dropbox or whatever, that are just generic "syncing" tools, Obsidian Sync has been built to provide the best experience with Obsidian.

I'm talking more about the plugin architecture not about the file format or third-party applications. sync plugins seems to be pretty limited compared to what's offered for a subscription.