system
Given the following post, respond as if you're commenting on Reddit:
human
If we know that the CMB was emitted when the universe was approximately 380,000 years old, why don't we know the precise age of the universe beyond its current estimate of 13.798±0.037 billion years?

Shouldn't we be able to know the precise age of the universe within a few hundred thousand years. Not within tens of millions of years?
gpt
how long after the big bang was the cmb created and how long it's been since then are two different questions.  the first is explained with particle physics, while the second is verified through observation.

plus error bars of 10% are considered decent in many fields of astronomy, especially observational cosmology.  so the result you quoted is pretty damn good.