Alright, I'll make a list as in why support is just as technically sophisticated as other roles.
-You need to know how last hit with very low AD (unless youre thresh) so not to push the lane and deny your ADC farm.
~Understanding when to shove the lane to deny your enemy EXP and gold is extremely important as well
~Keep track of how many minions die while the enemy is in EXP range and know when theyre gonna hit 2
~Why or When you need to ward their or your lane bush
-You need to understand when to ward and where.
~You cant go warding whiling your ADC is pushing a wave or you will miss EXP and your potentially vulnerable ADC will be exposed to lane ganks while shoving.
~Understanding where and why a ward is placed. Why ward your blue if your jungle entrances are warded? Does the enemy have a ward nearby and knows where you placed yours now? Junglers will work around your wards now
-As a support it is YOUR job to deny the enemy support from harassing your ADC. It is also your job to prevent the enemy ADC from farming and getting exp.
~You need to know champions synergies at level 2, 3, 5 and 6.
~Understand your champions limits and ability to harass and zone in a 1v2 situation
~Pay attention to the map and keep track of the enemy jungler and mid laner.
~Knowing your ADCs limits and how the enemy jungler will take advantage of that. (do you have an immobile adc vs a panth? play back at 6, ask the jungler to deep ward their bottom jungle)
-Positioning is everything for a support. Almost every support has a different spot the need to stand in relative to the team. Playing soraka? Stand behind your back-line. Playing thresh? Stand between your back-line and front line. And so on.
~You need to keep track of your cooldowns and the enemies to understand their threat level. If the enemy malph just unloaded his kit into your tank then dont waste your time CCing and peeling him when the enemies Vi is charging at your ADC.
-Utilizing your minimal income as efficiently as possible. While not all support items are that great, they are cheap and give great stats for that cost.
-The enemy will, in fact, focus a support. Unless theyre a tank support, youre gonna be squishy and will likely die to just about any AoE by accident if you dont position right. Do you really think a competent enemy team will just let a 1900 health soraka make her 1800 health ADC have an effective 4000 health? Why would i let the janna who is giving my enemy 8% MS, heal per second and a rather large shield live?
-You need to know when to and where to ward post laning phase. Warding the enemies red when theyre pushing into your base is nearly pointless. You cant just go out and ward while a team fight is about to happen.
-Whats the enemy team? Do they have a fiddle? Do they have something obnoxious thats gonna fly over a wall and CC lock someone? Where will 3 wards need to go to prevent that Warwick from coming from the fog of war? Does someone on my team have teleport and could use a ward to help us secure dragon/baron?
-What is the next objective that needs to be pushed? Where will my 3 wards need to go to help secure this objective?
-Who is the largest threat to my ADC and APC?
-What item order should i go? what will be more useful at XX:XX time?
Im sure i missed a bunch of stuff and im sure you probably wont even read this, but you know. Supports suck am i right?
Edit: If you feel my list isnt convincing enough ill be happy to add more.