overall, I think the problem cant be confined to supports alone, because the role itself does not function without another person in lane, sure there are support champions who can function out of the support role but if talking about the role and not the champions then you have to include the other person in the lane.
ADC's blame supports for very tiny things like not being able to go in because they lack the movement of their adc counterpart, not the supports fault.
The bottom lane as a whole can have the most active wards up at any time being between 2 and 4 (if the support buys sight stone) while other lanes can only have a max of 2 wards active at once (again if the money is spent of SS or a pink ward). it is not the supports job to place all 4 of those wards.
Supports for some reason are thought of as ward bots, yeah they tend to have the most but are still capped at 3 regular and 1 pink like everyone else not sure that number covers the map.
Supports tend to have the lowest gold income of the game, even more so if their lane gets camped or they play against a bad matchup.
the current domination of mages in bot lane as "supports" does not translate into supports don't know how to play, it translates into people cant play support so they play mages for a kill lane (some mages are classed as supports they are still included in this)
All supports are different, you pick a support that reflects your playstyle, this is the same as adc's, you wouldn't play an adc you aren't comfortable with and you shouldn't expect your support to do that either (my weakness is janna and nami)