I personally like lethal tempo as well, however, the reason I picked Fleet Footwork as the main rune for this guide is that Fleet Footwork offers Jinx help not just in combat situations, but also in laning phase which is her weakest point. In most games, I prefer to take Fleet Footwork for this reason, but I agree that lethal tempo can be a very strong keystone on Jinx. However, I only take it when I am certain I will not have any issues in the laning phase.

As for Stormrazor, believe me, I have not been a fan of it since it came out either. I really miss the old crit builds :( But the reason that pros/high Elo players always rush Stormrazor on champs like Jinx is that if you chose to go Hurricane > Infinity Edge instead, it would take a long time to build up stats because of just how expensive those two items. Stormrazor is a cheap and efficient item. Though in rare cases where I'm huge on Jinx, I like to go BF Sword > Hurricane > Infinity Edge and skip Stormrazor all together :)

My build is based off of what is the "standard" in Diamond+, though there are always exceptions to what's most common!

And thank you! If there is more you disagree with, I would be happy to discuss and hear your opinion :D It is appreciated