I mean, enchanters were strong solely due to ardent being op, and otherwise were fine and had a good support playstyle.
Tank supports should be able to solo kill the adc early on - the adc only has auto damage (consistent damage, no ability to make up for downtime with a burst of damage when up), while tank supports have good cc to counter that. They also have strong base stats because they're not meant to scale. It makes loads of sense, and if they don't get fed they're a real weak front line as they don't become super tanks like jungle or top lane tanks do. There's a reason why Leona or Braum engage with ultimate but then use their other abilities to peel in a full teamfight (obviously they'll follow up with more engage if they're getting a pick or the team is way ahead), whereas a Sejuani or Maokai will engage with ultimate and proceed to dive the enemy team (Braum may not be the best example, but you get the point, tank supports do more peeling than engaging because they're not tanky enough to survive back line damage in the late game).
Carry supports are ridiculous though. Brand/Lux/Zyra and company consistently dealing the most damage on the map from the support role is ridiculous. Lux support does more damage than Lux mid despite less income because it's an extra champion on the enemy team that needs to be prioritized and denied damage, when most teams simply don't have the resources to do that. They're not op individually, but forcing attention onto another carry that can still function and deal huge damage despite low gold income is a big problem. If they were only successful when they got 4 kills on themselves in lane (and not on the adc instead) that'd be fine. They can go 0/0/1 in lane and still be a huge damage threat with no gold though, that's just not right.