And there was a time when using libraries and frameworks was the right thing to do, for that very reason. But LLMs have the equivalent of way more experience than any single programmer, and can generate just the bit of code that you actually need, without having to include the whole framework.
As someone who’s built a lot of frontend frameworks this isn’t what I’ve found. Instead I’ve found that you end up with the middle ground choice which while effective is no better than the externally maintained library of choice. The reason to build your own framework is so it’s tailor suited to your use cases. The architecting required to do that LLMs can help with but you have to guide them and to guide them you need expertise.