We're all ultimately just learning what we need to to get the job done. After 20 years programming, it is very clear that nobody knows everything. Everyone just knows their own little slice of the software world, and even then you have to 'use it or loose it'. If you're feeling imposter syndrome, keep a study side project going where you don't use any AI, something like NAND to Tetris that forces you to learn low level concepts, and then just stay productive using AI for the rest of your work.