As a writer of film scores Williams is overrated IMO. Brilliant, but overated. Ennio Morricone and Bernard Hermann are the greatest ever composers of film scores. Every score they did featured a whole new soundscape of different instruments and emotional depths.
The linking scores in Williams work are usually a rehash of everything he's done before. Star Wars, Harry Potter, Indiana Jones, Jurassic Park are so similar.
But what Williams does best is themes, the main themes he creates are iconic from Jaws, to Raiders, Harry Potter, Superman, Jurassic Park, to even Duel Of The Fates. Ask anybody and I bet they could hum at least 4 or 5 straight off. You can't say that about any other composer. Even Beethoven or Mozart.
As long as he gets the time to write a few truelly great themes, all will be well. A war theme, a love theme, an evil theme, an action theme and a sad theme etc and we're cooking. It wouldn't be Star Wars without John Williams.