Everyone needs to be challenged now and then, it seems. Being attacked makes one respond, or might make one respond. And that response can be transforming.
Shostakovich was almost certainly a better composer after Stalin had given him his philistine going-over following the first performances of Lady Macbeth of Mtsensk, than he would have been if Stalin had left him alone. Although both are very fine, I prefer Symphony Number 5 ("A Soviet Artist's Reply to Just Criticism") to Symphony Number 4.
Had Shostakovich continued unmolested along the musical path he was traveling before Stalin's denunciation of him, I don't think he would merely have become just another boring sub-Schoenbergian modernist. He was too interesting a composer for that already. But I do not think his subsequent music would have stirred the heart in the way his actual subsequent music actually does stir mine, and I do not think I am the only one who feels this way.
Thanks to Stalin, if that is an excusable phrase, Shostakovich was forced to write what is now called 'crossover' music, that is, music which is just about entitled to remain in the classical racks in the shops, but which also gives the bourgeoisie, such as me, something to sing along to and get excited about. Shostakovich had always written film music as well as the serious stuff. What Stalin and his attack dogs did was force him to combine the two styles. He might well have ended up doing this anyway, but who can be sure?
What Stalin also did for Shostakovich was to make his music matter more. Thanks to Stalin (that phrase again!) every note composed by Shostakovich became a matter of life and death - while it was being composed, and whenever you listen to it.
Stalin turned Shostakovich into a kind of musical gladiator, a man who knew that every day might be his last. Not many composers get that kind of intense attention....