I was learning AI for months… but couldn’t build anything

For sure the approach matters a lot. Having some results that you can show while progressing keep the person motivated. Additionally, you can later on reflect on your progress. Nevertheless ML/DL can feel like a big puzzle at the very beginning. Unless you study it at University, you have to find a correct path to build a good mathematical foundation and sequentially learn about architectures, optimization etc. Best of luck to you!