It's how you use the 'support". We can support with anyyyyyy champion basically. Lux is good early game for the poke and early kills if she lands her skills... falls off mid-late, as if shes being a suppport and NOT taking kills, her dmg will be low, which in mid-late game will mark out one of her best factors- her poke.
Yet, if she gets fed as supp, her role usually changes to ap mage. Ppl will start to build full ap items on her, as her full potential kit isn't good with utility items. She's more like a 'kill set up' support, her poke is prob the best thing about her. combo Q, E, R then team can go in to finish the kill, that's if theyre not dead already from the R.
But most people agree shes not a good supp bc her Peeling consists of 2 high cool down and very thin skill-shots- unreliable. If enemy sees that lux missed her snare, shes probably dead.
-most lux supports (esp in low elo) don't buy SS which is why ppl hate lux sup as well.
I play lux supp in norms a lot bc it's just plain FUN And even a couple ranks already (I do buy SS btw)--- and I can truly say there's been too many times I couldnt do much to save my carry :_(
It's either get your carry suuupah fed *early game to snowball, or have to face falling off as a sup and being a side mage with low dmg mid-late game.
I agree that lux has good burst as a supp like annie and zyra. But There's more reliance on annie and zyra than lux.
Annie has a stun she can activate easily by using her 4 skills, plus tibbers can AOE stun a whole team. there's good CC in that.
Zyra is prob the closest supp to lux, but better. Her plants and ulty has AOE, plants that can slow, also she can zone out ppl with her plants dmg. Build rylais on zyra and op. Yet if youre out of seeds, it's going to be almost impossible to peel for the carry. Build ap items on zyra? Ppl usually don't mind bc she uses her damage to zone and that's already like CC.