Yeah, I've seen Age of Ultron twice now. Neither Coulson, nor any reference to anything going on in the SLIGHTEST about Agents of Shield, is mentioned in even the smallest bit. The movies act like Maria Hill runs SHIELD. Or, at the least, Captain America. The only thing brought into the movie is the helicarrier, which is made out to be something Nick Fury did himself.
You mention the Defenders, but that's not proof of anything - it's not a movie, it's a (potential) Netflix miniseries. I hope you can appreciate that's not on the same level as when I talk about movies in the context of Age of Ultron, which is set to enter into the top five highest grossing films of all time. Nothing to date has given any indication that what we've seen in any of the television or alternate source media will have any role in the major films.
And you missed the point. Coulson didn't appear in Age of Ultron because the continuity demands so, But, He was the one who constructed the helicarrier and he was the one who found Strucker's location. The secrecy is something the continuity demands, That's why The Avengers think that Fury was the one who built it. Just because something is kept a secret for now doesn't mean that it didn't happen. There's no TV continuity and Movies continuity, There's one giant, Fat marvel continuity.
The Defenders as a comics was a strong and big arch and it will also be a strong and vast Television arch. Four series, One miniseries. Just like the movies' phase slots. The first season of Daredevil introduced one of Marvel's most iconic villains, The Kingpin, That i don't think his story is over yet. And Daredevil's second season is most likely to feature Spider-Man as well as the two have a history in the comics. But things are just starting to warm up and you can't just throw them at the big arch without them fully exploring their stories first. That's what Marvel did originally with Iron Man, Hulk, Thor and Cap. Black Widow and Hawkeye are parts of S.H.I.E.L.D., Which was essentially the key player in the first avengers movie. That's why they didn't get their own introductory movies. And actually, When Coulson was talking to Skye about the anonymity of her team, It was a clear foreshadowing to me, That this will be a big part of the plot of the Civil War. As well as The Inhumans movie. It's still just a theory, That even Clark Gregg himself believes that it would happen. He said so lately. I think it's pretty obvious. Also, my theories about The Inhumans and The Clairvoyant have been two major successes. So, We will wait and see. Point is, You can't just force something to happen in a fictional continuity, Everything has to be fluid and natural. In order for the continuity to flourish.
P.S: Age of Ultron being one of the highest grossing movies of all times has nothing to do with its role in the continuity.