How did supports reach a point where they have become item dependent to function optimally?

People are worried about the changes to support itemization on the PBE.

I do think these changes need to go through for supports to matter in their choice of champion instead of the items you build on them. Last season was pretty bad with this as it just ended up being abusing ardent censor, knight's vow or redemption. Items on supports used to be a luxury but Riot then released items with very strong item actives but tend to give very little in terms of stats. With other changes which gave champions even more ambient gold without needing to get kills just made it easier for supports to get items. Supports can actually build items now. This sounds good in theory but it takes away from the identity of the champion and more towards the items. It just makes champions more identical instead of unique.

As of now if they released the current items as it is. It's not going to be good and I'm hoping Riot has more things to bring to PBE that can fix the class as it is. Some champions really need reworks and put their power back into the champion and not the items themselves. This has been a problem that has never been addressed at all since season 4.