I think the idea of 'junior' needs to be refined a bit. By the time I got my first job I've been coding for years, and have built rather substantial things. In fact, in terms of pure coding ability, I was probably past the initial, fast part of my growth.

As should have others, which the university education system should have made sure.

The fact that some people come out of 4+ years of software engineering education utterly clueless means that they somehow managed to dodge having to build anything, I think means that they will never get good at any point in time, as they either were very talented at dodging having to build things, and I don't think that talent is going to abandon them, or they couldn't really grasp the basics in an environment designed for just that.

With that said, I think you can see for most juniors, what you can expect out of them in terms of pure coding ability - sure a lot of them have room to grow, but I've met so many great people who were very young, yet were useful from day one.

In fact, if you have the willingness to grind away at some problem, that puts you ahead of a significant amount of the pack. I have had the misfortune of working with people who lacked any demonstrable skill, and had coping strategies for having to deal with any sort of hardship. Getting useful work out of them was a challenge in of itself.

These people managed to get the years in to be considered senior, and are probably dispensing their wisdom 'mentoring' juniors somewhere else, and are no longer expected to actually contribute to meaningful issues.