Time. It is time intensive to learn but like DHH said, its not nuclear science. Its not that hard. I'm not sure what you are doing now but just running a VPS that isn't managed is a good start if you aren't already doing that. Its really a spectrum. Most people don't need AWS IMO. I have nothing against AWS. I've used it and I still use it for a couple things.

I feel like I've come full circle. My first job in IT was managing some websites on a Linux server. I was so green. I've went from that to managed hosting, to AWS, to Serverless, to decoupled systems, and back to self-hosting many of my own apps for personal use. I find it enjoyable now. There are so many tools that make it easier that didn't exist in the 2000s.