Yes, 千字文 is not common in mainland China at all. I was born and raised in mainland China, and have no memory of the content of 千字文 other than the title.

三字经 on the contrary, is ubiquitous. I am guessing everyone heard of the first 2 terms of 三字经: 人之初 性本善, meaning "the human nature is good"

This can be seen as a foundational psychology imprint of relatively dossile personality on every Chinese.

Nowadays, I always get a vibe of Dune when reading Chinese ancient classics. What a monumental accumulation of human cultivation in those classics!

Despite communism transformation, China actually get back to its traditional way of thinking and dealing with the outsiders around the world.

Or a different interpretation: the conventional mandate of heaven returned, but with a communism decoration.