Many of the things I once thought were trivial I now think are important. That is, I used to think they were trivial in the modern sense of being unimportant. Now I think they’re trivial in the classical sense of being foundational (from trivium, the first stage of a classical education).
In business, “trivial” means “vitally important if you’re actually doing the work, but not important if you’re just watching.”
Related link: Very applied math