Yes and no. It was easy for Bach and Beethoven to be innovative, less had been
done back then. The story of classical music from 1800 to 1952, though, is a story of composers forever looking for new ways to innovate. First they did away with all the old rules of structure, and we didn't miss them too much. There's some great music from this period.
Then, they started doing away with all the rules of harmony. The prelude of Wagner's Tristan und Isolde has a dissonant chord which resolves to another dissonant chord, and it totally blew everybody's mind. By 1913 you've got The Rite Of Spring which avoids almost all traditional harmonies, and it's causing riots in Paris but a few years later that kind of thing is old hat. In the 1920s you've got Schoenberg going "Y'know what? Screw tonality. Let's just play all the notes one by one; at this point you've got music which very, very few people out there can actually enjoy. I mean, I have a CD of Schoenberg's violin concerto, and even the blurb on the back of the CD doesn't seem to like it very much.
Then you've got a few decades of increasingly obscure music until my chosen endpoint of 1952, which is the year when Johnny Cage wins a flawless victory in the "look how unmusical I can make my music" championship by publishing 4'33", the piece consisting entirely of silence. This was the signal that the old musical tradition had finally disappeared up its own butthole. (1952 is also the year when Rock Around The Clock was first written.)
Anyway, John Williams is basically an acknowledgement that if you're going to make big orchestral music which people actually like, then all the good ideas were taken by 150 years ago, and any additional innovation away from that point pretty much just makes it worse [or, at least, less enjoyable by the majority of people].