The support role is so unpopular because you need to be able to do a lot with very little.
Your income is much smaller than the rest of the lanes and jungler, therefor what you can buy and at what point in the game you can get it is limited. On top of that, you absolutely need to buy a Sightstone and Oracle Alteration for a variety of reasons. Vision, true vision, map control, etc. Full builds on supports are rare, and that also makes the eye items not as enticing anymore. Slot efficiency isn't our problem.
Not only that, but you need to trust a complete stranger, who usually is a diva that only uses their trinket early game when they forget to ban Blitzcrank. Seriously though, nobody likes how tied to the ADC supports are, and yes there are ways around it, but a huge chunk of your potential is tied to how well your ADC does. To a lesser extent this is true for ADCs, but they still have damage, which means so much in this game. If a support gets someone who is off their game (happens to all of us), then that's a huge blow towards their chances of winning. It's not impossible to come back from a unfortunate ADC plays bot lane, but should it be that difficult for the support? I often see ADCs carry their medicore support with sheer damage. I don't see that happen as often in the reverse.
Then you are always 1-3 levels behind everyone else except the enemy support. This is the worst thing in my opinion. I hate seeing games where I recognize what I have done, even my teammates do, and yet it just doesn't show. I'm still a level behind the enemy 0/5/1 Sion with mediocre farm. How messed up is that?
I don't need players to recognize my hard work. I want the game to do that.
Supports do get blamed a lot for crap that's not in our control, way more than any other role. I don't care what anyone says about that. I don't care about the same 3 support mains that come on here and claim everything is sunshine and roses 99% of the time. It ain't. I've been to Gold, and it's not better, however I can't speak for any higher than that aside from what I see on streams. The highest friend I have that mains support is in Platinum, but the vast majority of us are Gold are below anyways. Overall, I do see supports get the most BS from their teammates. That's just the way it is folks, and it is actually not that hard to understand why they do when you take into consideration everything about the Support role. It is understandable that they're the most likely to get blamed. Players love passing the blame in MOBAs.
But you know what? That really doesn't bother me. The mute button exists and the likelihood of you running into that fool again is slim. That person that criticizes you for being 0/4 when your full score is 0/4/15 likely isn't going to make it very far, and if they do they'll look back on that moment and cringe. Same with the people who talk about there being no wards on the map when they've only put out 2 or 3 the whole game. The support is always the easiest scapegoat because the score doesn't always reflect our influence on the game.
Let's just be honest about that, okay? I don't think that is the reason people give up on the Support role though. If people quit just because of toxic behavior, LoL would have died ages ago along with every other MOBA. Supports may get more of it, but you can come across toxic behavior in every role.
That's not to say there aren't bad supports, but honestly? Playing a basic functioning support isn't that difficult. Rarely have I seen it played "badly." Meaning they don't even do the bare minimum. I've seen many supports casually sit there, babysit, and ward. When your ADC is demolishing the enemy on their own, that's enough to keep them going. You won't make any amazing plays etc., but I get why people can see that we don't do much when that's a huge chunk of supports I come across. It just won't be enough against a support and ADC that both are actively participating in the game. Half the time that doesn't happen. There just aren't that many true support mains in ranked for the reasons I just listed.
Moving up playing as a traditional support is difficult. If you have good teammates, you can make them great. If you have bad ones, then they usually aren't going to be able to use your abilities to their full potential, which impacts you so heavily. Turning the tides of the game isn't as clear cut as it is with the other roles and you need to be resourceful. You do need to put in a lot more thought to make something like that occur because you do less damage and are usually levels behind. Sometimes I don't think it is possible to do that as Support because the role is so team reliant. In Gold or below you can kill everything or farm and make decent progress. That's not to say you should, because certainly not all games are that one sided, but It is much more simple. If your concern is simply making fast progress in ranked, then I wouldn't look at the support role either.