Lux support is a troll pick in ranked

Lux isn't a bad champion herself but picking her as a support is just a troll pick at this point just like picking Tahm Kench is. Tahm Kench is probably better than Lux support.

Her W offers a very small shield initially and has a long time to land its bigger one while being a huge telegraphed skillshot. Her Q is a telegraphed, slow spell that can easily be blocked by minions or dodged or predicted due to the champion animation. She's squishier than a fly on the wall.

Once you miss your Q, the opponent can literally just walk to you and end the game.

Winning as Lux relies on your opponent purposefully just running it down on you without knowing how the game works. She's destroyed so easily by the rest of the support roster and basically is a free intfest when there's a hook support or Leona on the other side.

It is also important to state her kit synergy with other ADCs is horrid.

Playing what you want is perfectly valid, but don't complain when you're 1/7 and your ADC doesn't engage because you don't know how many portals of weakness you opened. Usually, bot lane is won with whoever lands the first CC ability and auto because that initial damage just means they'll kill you sooner. And it's horrid for a squishy like Lux as she'll die pretty fast. So when an ADC is auto'ing to take down the opponent and you die in 3 seconds, that's on you.

Your positioning is on you.

And for christ sakes, ward. Lux supports are too notorious for not warding or buying control wards. Nowadays, they're the toxic versions of Vayne/Riven/Yasuo players except there's no mechanical difficulty to your champion to excuse you.