A couple criticisms. The cult of tradition and The USSR rejecting modernity? That’s clearly not true. From art to science, Soviet principles were about not just rejecting the old ways but completely wiping them away. Mao took it to the extent of having the youth go around and cut the hair of elders who sported traditional fashion.

Soviets made a big show of being modern, but were positively moribund in traditional artistic mediums, and rejected many modern scientific ideas as bourgeois regardless of evidence. The realms in which the Sovs were most anti-traditionalist were that of new artistic mediums (with Soviets being pioneers in film, a medium that only barely and technically predates the Soviet Union in a serious sense) and in traditions that were rooted to institutions of society they didn't control, as all totalitarian states.

Secondly, Nazi as anti Christian was a post war invention to hide Christian complicity in Nazism and the Holocaust. Christians ran the Nazi schools. Hitler’s speech’s were straight from Martin Luther’s book, “On the Jews and their Lies.” In the private Table Talk interviews, Hitler talked about his dream of creating a German Christian church exactly like England has the church of England. He didn’t want to destroy Christianity. He believes he was saving it just like England had done. That private interview was intentionally edited and mistranslated after the war to portray Hitler as anti Christian.

Anti-traditional Christian, if you prefer. Nazism's position on Christianity was markedly different than, say, fascist Italy, or the clericalist fascist regimes Germany allied itself with, and the strong neo-pagan current in Nazism is not something that you would find prominent in other contemporary major fascist movements. It's fair for Umberto Eco to single it out.