ADCs buildpaths can also change fairly quickly in relation to other classes, though. Lethality, armor shred, crit, etc - it can all change with the new meta and do so in a blink of an eye. Most people wouldn't have thought of going BoTK on Ashe but now it's meta after it was buffed; chances are it won't be if it gets nerfed later on though. Until Runaans got buffed, the only adc that would really build it was Kalista - suddenly it became must-have for most adcs. I can't really think of a similiar 'must rush' items on most mages other than maybe... rod of ages when it got changed up and was super gold efficient than most other AP items at the time, I guess?
If they would change the tutorial so people aren't forced to build a thornmail on Ashe and something different like a BF sword and boots though, that might be a decent place to start.