I have no idea why you're bringing up pro teams, however supports have been credited to having the 'play making' role of the game in professional League since MadLife entered the scene and knew crazy stuff like enemy cooldown timers and was the dominant voice in the bot lane because he dictated the conditions of the game. MadLife isn't nearly as good currently as he used to be when he hit his peak, but you still hear about exceptional supports with great play in NA LCS like Lustboy.
Moving away from professional LCS since that is hardly relevant to either of us, I think support is the most demanding role of the game for Solo-Q because you have a couple of minutes to try to guess if you have good synergy with your ADC or can gauge how experienced they are at playing and minimizing risk if you don't have good cohesion or if your ADC is really into engaging in risky confrontations.
Thresh is the best support in Solo-Q for this very reason. He has a loaded kit. If your ADC doesn't understand that he's pushing his wave too far into unwarded and dangerous territory, you have the lantern to draw them back. If your ADC is just 1 v. 1'ing their ADC you can also throw out the lantern to give them a passive boost. You have a hard engage and you can also use the lantern to set up a team play. Your ultimate is a zoning tool. Everything about Thresh is created to fix everything that is wrong with your ADC. However other supports need to address all these points with their ADC. Some supports like Leona can only go "all-in" and your peel for your ADC is literally you going all-in on one target.
How can you say that supports have it easy when you have Vayne being one of the most common picks in Solo-Q which is literally like giving the entire team the middle finger and you're the one who has to take care of the baby until she is able to build four items. The problem with Solo-Q mentality is that if you die, it is your fault. So whenever Vayne gets low on health and the trade looks bad but you can pick up a double kill on her single death, she's going to condemn the target away from her just to save herself and not think about the bigger picture. Ezreal ADC? Tristana ADC?
"I'm going to go in but if things look bad I'm using my escape to get out."
They literally hit one auto and then they Arcane Shift out of there and if you're a Leona you just went all in and are getting gang banged simply because their jungler entered the edge of your screen. However, since your ADC sprinted away faster than Lucian you get all the CC and **** damage while your ADC stands by tower with full health and can't do jack **** anyway in a 1 v. 3 yet reminds you that you died because it was a bad engage.
Did you use your Mikael's at the right time? How about your Locket? What about Talisman or Righteous Glory? Not to mention landing your abilities at the right time in order to set up an engage. An ADC's role in a fight is to often follow up on the play made by a support. However, if the support isn't able to set up an engage situation then the ADC cannot fulfill their role optimally. The only reason why supports don't seem to have that much requirements in Solo-Q is because there is no expectation for someone else to actually support for you in Solo-Q which is why it seems like support has low level responsibilities.
Tbh the ADC's I've played with don't know bot lane match ups or don't give a **** about minimizing risk in a bad matchup. I've seen ADC's rush the same items like Infinity Edge or Blade of the Ruined King against a Sona or an Annie and their support is building Morello's or Athene's or some other item that is not Mikael's. And when it hits six the ADC gets cheesed by the ultimate and ultimately ends up dying and at the end of the game I never see a null-magic mantle anywhere in that inventory.
I agree with you that there are supports that don't know how to position or properly trade. Those are the ones that watch you die and offer you no peel when you get targeted. Time management? Since when is this ever a factor in the game aside from knowing above creep waves, camps, and dragon timers which every single member of the team should know or keep in mind. Grouping for fights/objectives, farming, kiting, and positioning to not take damage are all secondary factors you think for a support? There's a reason why your mains are Wukong and Zed, it's because you don't play support.
Funny thing is that ADC's benefit the most from having vision versus an ADC that has incomplete vision in a team fight. Factoring in that they are ranged marksmen means that being able to target or having first priority of target is significant in any trade. And if you think that a bad support is going to give you adequate vision and not burn all their wards on stupidly warding tri-bush or some other areas that are on the opposite side of the map as all the activities that are frequently occurring then you are naive. I have never felt as an ADC that the vision given by my support was adequate much less useful, sometimes I even question if they even used it over the course of getting new stacks from the item shop.