I think you're arguing that without good compiler authors, a typical application developer would be inherently unproductive. Which is true — compilers are necessary tools, and it's necessary that they be good.

But what I was suggesting is that one does not need to be capable of being both a compiler author and an application developer (if, for the sake of discussion, we avoid any semantic arguments and treat these as generally different things) to be of good value. I don't know how to, say, write a proper lexer, or write any assembly worth any salt at all, but I can write what I consider to be good, reliable application code at a reasonable level of productivity.