What is epoch-making must be people's understanding several years later, and it is people's understanding of history, not people's understanding of the present. And the longer it takes, the clearer people's understanding of epoch-making will be.
However, people can predict whether this era is epoch-making. Perhaps Einstein's general theory of relativity is an epoch-making event in the development of human society. Later generations have the right to comment on epoch-making events (because it is proved by the history of social development).