Handling dictionary validation issues in text-based tools?

I’m working on a small side project that involves validating user-generated words and I keep running into edge cases where legitimate words are flagged as invalid. I’ve noticed similar behavior in some lettersboxed.com, where the dictionary logic seems stricter than expected.

This made me wonder: when you’re building or testing text-driven logic (especially anything language-based), how do you usually handle dictionary completeness, regional variants, or updates over time?
Related to that, do you prefer embedding a static word list or relying on external sources, and how do you manage performance vs accuracy trade-offs?

Curious how others here approach this kind of issue in real projects.