I think we've detracted pretty far from way support itemization was supposed to work.
S2
Supports are item independant champions.
All they really need are boots, so they dedicate the rest of their income to utility items for the team (Sight wards, VIsion wards, Oracles Elixir).
They purchase 1-2 gold income items so they can afford more vision than the other support.
S3
Supports now have sightstone, so they need not spend their entire income on wards anymore. Several cheap utility items were added (Runic Bulwhark, Shard of True Ice
They're still item independent champions who spend a lot of money on wards, but now they can afford a couple cheap team utility items.
S4
Wards are capped per champion, GPM items are overhauled, Oracles is gone, vision wards are permanent, and trinkets are a thing.
Several cheap utility items now build directly out of your GPM item.
Supports can't spend their entire income on vision now, so they now have gold to spend on real items, but they still have low income.
Zyra and Brand start appearing in botlane at this point.
S6
Wards removed from the shop.
Supports are solidified as just building regular items instead of buying tons of things for the team.
The Zyra/Brand type of support is no longer troll, it's just normal.
S7
Quests added to support items, making them dangerous as hell.
S8
Sightstone removed.
Supports now only need to invest 850 gold or so into their role, plus 75 here and there for control wards, and then can build anything.
S10
You no longer need to spend any gold upgrading your GPM item.
Your role only requires 400 gold to be spent on supporting, before control wards.
It eventually becomes an item with roughly 2k gold in stats for only 350 gold, plus a warding active
We've gone from "low income, item independant champions who spend most of their income buying things needed for the team" to "medium income champions with a massively efficient 400 gold stat stick".