They're juniors. With that kind of mentality, I'm not sure you're looking for juniors, but instead are looking for someone with a few years in industry that is apparently masquerading as a junior. But perhaps my expectation of "real systems" is different than yours.
To put this into perspective, I mentor and have mentored lots of juniors from code schools and traditional, four year university computer science majors in web dev. Having some concept of both the web stack/language and a basic understanding of good coding practices is about the most I'd expect. All thing things that sit on top of it, like scaling the stack, performance optimizations and the like are things I wouldn't even come close to expecting a junior to know. Those are things I'd expect to have to coach on.