Making your own framework is great if you're in no hurry at all - maybe you want to learn, or maybe that's part of what you're selling. For everyone else, use the approach that gives you the most leverage.
Not only does it not know everything you know, you don't know what it does and doesn't know, and can't find out thoroughly enough to know that you know what it does and doesn't know. So you can't cover all the bases you can cover by just using some code.
You also won't reliably get the lessons it does know out of it every time, because it's a non-deterministic system.
Worse, LLMs are being replaced all the time. The next generation might be trained forget stuff because memory efficiency and also, hey - it can just go look up online what it doesn't know about! Yep - that's definitely gonna be true until the end of time!
You would be blown away by this wild thing called determinism!