Music theory is not rules. It is a vocabulary.
When someone says "that chord is a ii-V-I," they're not saying "that's correct." They're saying "I recognize that shape, I know where it comes from, I know where it's likely to go."
Theory lets you name what you're hearing. Naming is the first step to understanding.
The trap is mistaking the map for the territory. ↗ @alice / on-linking-ideas says something similar about note systems.