Like the title asks, I've been seeing a ton of passive adc players, and as a support main it's been difficult to decide who to play as in order to help them out more. Any tips would be appreciated, and please refrain from comments like "get gud lol". Appreciated and thank you.
Just carry the game, no one gives a fuck about peeling
I always like Sona and rakan as a support if im playing passive
Nami. She'll heal any poke coming their way, if you're good at landing bubbles then you're god and her ult is amazing engage and probably the best disengage in the game. She'll protect the ADC and easily transition into mid/late game
honestly id suggest picking up nami, she can be played aggro and passive applys alot of pressure with her w poke and her all in is pretty good to
In lower Elo I'd play something that can create peel or carry. And I mean peel for yourself not the ADC. Since your S5, ADCs either tend to be passive to the point they won't engage, or hyper agressive to the point where you're always going in. Janna, Brand, Rakan, Sona, Nami, Karma, and maybe even Leona (Leo specifically for team fights) she's really good right now with her W and Aftershock. If you're looking to climb getting good with any of these champs would benefit you :) Just depends on your playstyle, and who you're comfortable with. Meta doesn't matter in low elo.
Your matchup / pressure from jungle and mid on you should dictate how you play more than anything else.
You can force aggression pretty easily- it's hard to ignore a 
engage- just make sure your adc's in range to follow up, if they don't have the reactionspeed of dialup internet you can stomp. (no ADC will ever click the lantern dude, don't bother.)
Being aggressive with 
can end up as a more solo experience. You can pull it off but limit yourself- if your ADC is making you 1v1 and you're getting nothing from it, give up and save mana. These guys ARE actually 'poke supports' (Bard can even be hard-enage) so I don't encourage fully defensive play in winning matchups, 'cuz honestly you're not using their whole kit if you play 100% defensive if you don't have to.
If you want to play 100% defensive while maximizing use of a kit, start looking at 
.
When I was a lower MMR (below average, when I was newish) I would ask every lobby how my AD wanted to play. They were pretty honest, so don't be shy about doing it.
And I know everyone's joking about it, but if your ADCs are so passive they won't auto someone who's in range, play 
. That's not an 'attack damage carry' that's a CS sponge.
Oh and ping 'OMW' 'assist me' and target people when you're about to go in, helps massively.
If you're agressive in lane yourself.
don't forget your support item, after that build what you want. 
make their adc solo engage on you, they'll be forced to react, if they don't build AP/HP/Mana items.
If you wanna just sit back
Janna and soraka and lulu come to mind.these are traditional supports and have no problem sitting in lane and avoiding conflict. However they can be boring so if you want a little bit of play making potential go for something like braum nami or taric. They have great peeling while also having some aggressive abilities. Im not sure what you mean by "helping them out more" but if you mean setting them up for kills, champions like thresh blitzcrank pyke and zyra are great at doing so. Hope this helped.
Enchanters(like Lulu, whose ult and skippy enciurage passive adc players to find comfort in playing offensively) or Supports who can carry(like , just please, don't take the 1st one it's tilting when they go dorans ring instead of spellthief's edge).
Enchanters in general, aside from the main three Wife In Lantern mentioned I'd add Sona to the list too.
