My Apple Watch unlocks all of my Macs. When I join a new WiFi network on my iPhone, those credentials are immediately available to my iPad. When my iPhone rings, it pauses video playing on my Apple TV until I ignore the call. To send a link from my iPad to a friend on WhatsApp, I can copy the link on my iPad and paste it into WhatsApp on my iPhone - automatically. I can use my iPhone as a remote camera to insert a photo into a Notes document on my Mac with one action. The list goes on.
Yes, there are absolutely problems and Apple has made some dumb choices (I don't mind the butterfly keyboards but I hate the razor-sharp palmrests...), but overall it's incredibly cohesive in a way that I feel lots of people don't really grasp.