I dont know if that is really true. Normally the support mains I know have skin as thick as the earth crust, and are more jolly then Santa. Usually people hate being the ADC's bitch and team punching bag for the loss is why I would say people dont like it. Some of the best play makers in the pro scene are Supports like Aphromoon, they just usually dont get the credit because the ADC was given the kills even though they did all the work, which also is tough for some players because if I am 1/0/27 on a support why is the 8/0/3 ADC getting the credit for the carry?
I do agree with you that currently though a lot of the good supports are brain dead, but so is a lot of the lanes except mid basically imo (Jungle main). Supports like Thresh require a lot of skill similar to champs like Nid, lee, Vayne, Riven ect. It's just people choose not to do it because they want their peers to praise them, which franky most people dont.