Modern Java is vastly more complicated than early Java. So I'm not sure I follow your reasoning. Programming nowadays is absurdly complicated. I have 20 years of experience and I can't imagine how new developer could learn it all.

I don't really know if AI makes programming easier or harder. At one side, you can explore any topic with AI. This is super powerful ability when it comes to learning. At another side, the temptation to offload your work to AI is big and if you do that, you'll learn nothing. So it comes down to a person type, I guess. Some people will use AI to learn and some people will use AI to avoid learning, both behaviours are empowered.

I have simple and useless answer how to solve that. Throw it all out. Start from the scratch. Start with simple CPU. Start with simple OS. Start with simple protocols. Do not write frameworks. Make the number of layers between your code and hardware as small as possible. So it's actually possible to understand it all. Right now the number of abstraction layers is too big. Of course nobody's going to do that, people will put more abstraction layers and it'll work, it always works. But that sucks. Software stack was much simpler 20-30 years ago. We didn't even had source control, I was the young developer who introduced subversion into our company, but we still delivered useful software.