For every one of these stories there are two ways it can go: The first is it turns out the senior dev is jaundiced in their view and the problem was improvable/

For every one of these stories there are two ways it can go: The first is it turns out the senior dev is jaundiced in their view and the problem was improvable/fixable, or thee senior dev is right and the junior dev is about to go and waste a whole load of time on something they've already been told is a waste of time. As a manager I always hated these situations, firstly, because the problem the juinor dev is trying to fix is almost never as productive as "Hey let's upgrade to python3", it's more like "Hey let's migrate to this specific version of this specific tool that I happened to use on one of my pet projects" or "I've got this incredibly ambitious plan to change everything about this peice of code you gave me to work on" (You're only looking at that code at all because it's simple, relatively unimportant and we're trying to ease you into the team). The problem is if it is the junior dev whose wrong you're now going to start seeing all these new issues because you've taken someone whose intuition isn't quite there yet and given them something incredibly complex to do. That's when you get into work 2 weeks later and find their mega-commit changing 2,395 files changing tabs to spaces and auto-modifying everything to camel case. Taking a chance on that intern's pet project means a lot of support from others in the team.