Maybe Sightstone should be removed. Hear me out.
In the past, vision was optional. Riot just put wards in the shop and let players figure out how to best use it, or not. So of course we made the support buy most of them and it was terrible mostly in solo queue where it took away individual player agency unless the support decided not to be a team player. So that's why we have trinkets.
Sightstone is a remnant of the old way. The support player is expected to spend gold, an item slot, and give up early stats to get it. This takes away player agency. The support player either gives up agency or isn't a team player.
I just had two games in a row where our support didn't buy a sightstone and we had a vision problem because the enemy team had better vision. I don't like to be that guy who tells another player what to do, but what else can you do? If you want to win you have to point out problems and try to fix them. This situation is frustrating for everyone. It's really hard to play when the other team has a vision advantage. Its also frustrating to know that it's because one person on your team decided to be selfish. It's frustrating for the support to be expected to buy a boring item that doesn't actually do anything cool.
I liked the move to trinkets because it basically forces players to have vision capabilities. The problem is we still depend on the support to provide additional vision if they feel like it. It shouldn't be like that. We should have a reasonable amount of wards available to the team as a baseline and additional vision should be in things like Frost Queen's Claim, scouting tools.
PS - can we also get a consumable slot for control wards?