Modern LLMs evolved from translation models, and they still seem to work best at translation-shaped problems. Even if you are asking them to translate specs to code, or code for system A to code for system B.
In my case, I added SQLite and Postgres adapters to a formerly MongoDB-specific CMS, including support for a largely compatible API, "in one wild weekend..." followed by lots of verification. That was only practical because we already had a large test suite. But it was still a task that would have been out of the question for our team size before Opus 4.6 or so. Again, it was very much a translation-shaped problem.