A 53.55% win rate is relatively healthy. Blitzcrank and Katarina have been up high consistently with high pick rates as well, but you... well, you see a lot of Kat threads but Blitz threads are fewer.
I don't see what your point is. Riot's been fine with champions as long as they don't drop or rise 5% around the 50% mark. Sure, Jinx could use a little love tap, but other adcs could get a little love as well.
We're never going to have perfect balance. Champions will rise and fall in popularity, causing their win rates to flux as a result. Jinx might have a good win rate now, but if Rito buffed her counters or released a counter, it would likely fall.
And she's not number one. If you want to talk about balance with your kind of logic, you title should have been "Sejuani, Heimerdinger, Amumu, Sion, Blitzcrank, Malzahar, Jinx, Katarina, Volibear, Swain are balanced."
I mean, come on. That's just biased.
Highest Winrate/Pickrate out of all ADC's ✔
Insane turret pushing ✔
110% AOE crits/longer than trist's passive range ✔
Zap does insane damage while it has slow cc and gives off vision ✔
Lowest CD Projectile ult out of all the ADC"s which makes he spam it like crazy ✔
Instantly gains huge attack speed from one attack speed item ✔
BUT MUH MOBILITY
You got some popular jungle, support, and mid picks in that list too. Gonna complain about them as well?
Every adc is supposed to be good at taking turrets. MF has an AS steroid, and Trist can use a spell on turrets.
Those aoe crits cost mana and drain her bar if she spams them. Early game, this can be abused. She has no waveclear spells outside of this, like Caitlyn and other adc champions.
Zap can be blocked by minions. Many champions have ways to get vision (Kalista's roaming ghosts, Caitlyn's traps, etc).
I got nothing here. Sivir has an amazing teamfight ult, Ashe has a great cc initiation ult, Graves has high burst ult, Caitlyn has a "kill secure!" ult that cannot miss. Every adc ult is different, Jinx's is just a global execute. You could complain about Ezreal's ult, but nobody really does.
That's every adc, ever. Seriously. Jinx has to get autoattacks with her Q to amp her AS up, otherwise she has the lowest base attack speed of the entire class (meaning she can't spam rockets).
At least her passive doesn't activate until a kill or assist, whereas champions like 
get a mini-trinity force passive, 
can chase, 
gets tankier in a fight, and so on and so on (not going to even bring up Kalista).
