Honestly, I see good points in both of your comment sets.

But there really is a floor on how deeply a person can understand their own software. There has to be a "good enough" somewhere. As a C# dev, I can understand my entire codebase pretty deeply. And I've read enough of the .NET Core framework to understand some of the nuances of how a lot of the methods we rely on every day are implemented. But I've never once looked at the CIL that Roslyn has produced, and certainly not inspected the machine code that the runtime has compiled. I can't read or write Assembly. I don't really know anything about the x86 or ARM instruction sets. My understanding of the CPU is barely better than "it's transistors," and even lower than that, I have a vague awareness that neutrinos from space can flip bits and there are error correcting mechanisms for that, but I have no idea how they work. And yet, I'm able to write fast and reliable software.

There are super knowledgeable devs out there who pretty much DO understand the whole thing, but it's impossible to memorize every line of every version of framework that you're using or the unique alterations and upgrades to every piece of silicon that your program will run on, and as you guys pointed out, proprietary operating systems are basically completely opaque to our understanding.

So the question is really "where is the practical floor that you stand on?" And for me, personally, there is room for at least some areas of code at the application level that I'm OK with never having read myself.