Yo, i'm playing league for the 3rd year as support main (got to s1 at my best this season), but i quit the role and going mid. I'd rather start all over then put my lp and faith on that lane. Obviously there's a ton of reasons why ppl aren't too eager to be supports, auto-fill being best proof that the problem is real.
I want to however add one more, rarely mentioned yet very solid reason why support is such a bad role to climb.
**It lacks a concrete framework for a player to work with**.
When you go mid, your mission is clear - grab your favourite midlaner champ, farm up, don't feed, and depending on matchup either go kill mode on enemy laner or just play farm lane and look to roam. It's clear, it's simple, it's easy to see what needs to be improved and what your job is in general.
1. Grab a champ ~~that you like~~ that is best suited to patch up the disaster that is your teamcomp (makes you hate your games).
2. Consider 3 other ppl botlane, both strengths and weaknesses of enemy botlane comp, as well as yours combined with adcs. Tons of thinking more then in solo lane.
3. Or don't because you got first or second pick. Heaven for other laners that want to lock in a contested pick, but a disaster for supports that should aim to counter enemy team comp, not be countered themselves.
4. Wave control is crucial for success, but down on bot there are 3 other ppl contesting that and you're in the back row, as it's the adc's job to manage his wave..
5. You don't know the skill level and playstyles of neither enemies nor your laner. In solo lane, it's you vs enemy. At least half of what's going on there is under your control. In bot - 1/4th. Especially a problem if you and adc are naturally mismatched - like you play aggressive engage, they ignore it and farm up, or vice-versa.
6. You're not allowed to cs, depriving you of skill crucial for playing in other lanes should the want/need come, save jungle (which on it's own is another very complex and ungrateful role at times).
I'm not saying climbing as support is impossible or that i'm a god support and failed, hell no. What I am saying is that solo lanes allow you much more freedom and control over the outcome of your lane matchup, while providing much better environment for OTP'ing a champ and truly getting the feeling of being on a path to mastery and steadily progressing in a given role on a champ you like.
So in general "it's do it my way and steady growth" vs the minefield that is being a support. It's no wonder there's a shortage of support mains and i see many troll picks from auto-filled ones almost every 2nd game, now that i left botlane and am training mid.