Quests only complicate things as much as the Support items already complicate things, since the Quests are just "do what you do with this item and get benefits".
As for the Quest rewards; Soraka's Movespeed buff is conditional (requires an ally to be low health) and she's probably going to be taking Ancient Coin, not Spellthief's Edge. Janna's movespeed is largely passive, and, while she'd probably also take Ancient Coin - she would still partially benefit from Spellthief's' movespeed buff on-spell-hit. As for Bard, his movement speed buff is tied to his Wanderer's Call Chimes, which are largely outside of lane; Spellthief's Edge will benefit him in-lane.
For Nami, Karma, Sona, and Lulu, I can give the point on, and readily agree that Spellthief's Edge movement speed may not ostensibly be a great buff, but it doesn't really need to be.
As for Braum, Thresh, and Blitzcrank (Thresh especially, as a lightweight Disruptor) - they can all greatly benefit from the passive shield from Relic Shield - it doesn't really matter that they have some shielding abilities of their own (Blitzcrank's Mana Barrier, Thresh's Dark Passage) or often take Courage of the Colossus - the Relic Shield quest's passive Shield will always be a benefit to them, as it increases their durability, allowing them to do their job.
As for the other issues (unaddressed by the items), I'm willing to argue a few. The first being Champion diversity; while there aren't really a ton of Support champions out there in comparison to most other roles, there's still a good handful you can pick from. Whether it's Utility Supports like Taric or Sona, Medics like Soraka, Enchanters like Lulu, Janna, and Nami, Disruptors like Thresh and Rakan, Vanguards like Braum and Leona, Guardians like Alistar and Tahm Kench - even Mage Supports such as Brand, Karma, Zyra, etc. all have a fair diversity with various levels of skill.
And with fun gameplay, I also have to point at a few of the Support champions mentioned; look at Leona, Tahm Kench, Alistar, Nami, and Zyra. Leona is a hard-engage lockdown tank, Tahm Kench is either someone's savior or the bane of their existence, Alistar is just crowd control for days, Nami is an entertaining Enchanter, and Zyra is an amazing zoning Champion with a unique playstyle. I'd be willing to argue that if you played all five of those Champions, at least one of them would be fun.
The Support Item changes aren't counter-productive, they're just one of many touches to try and impact the role to be more satisfying. Riot's been working on it for a while now, and I imagine they're still working on it, especially in the itemization department. I'd say they're doing a great job of it, personally. So, give the Support gold-gain items a chance, we'll see how they work once they hit live.
