I think it really is that unique - Notion blending read/write is pretty revolutionary for an app like this. Wiki's are obsessed with toggles between read/write mode.

Those apps you mention - Drupal, Wordpress, etc - have write modes that exist in backends with alien experiences to the read modes.

By unifying read/write into a single continuous UI, with built-in relational databases usable by non-technical users, Notion really does let people create damned powerful custom apps.

If you squint, you can see how Notion looks a lot like the next version of the Internet. By hyper-focusing on company intranets they miss out on the power of connected workspaces ("domains"), but the thinking is there.

I'll be seriously surprised if Notion isn't looked back on as a breakthrough paradigm shift.