Item Effects/Passive tutorials

So I find it extremely frustrating when players on my team, primarily the carries, do not build according to the match. From my experience most carries build a generic build every match and that doesn't really favor long term winning.

Matches of league are stable in terms of map play. The most variable factors in league matches are the champions and the players playing those champions.

What most carries do is build to the strengths of the champion they are playing. This is fine, but unfortunately doesn't help them against a wide swathe of champions (this is where the notion of counters come in). Honestly there is no such thing as a counter when a player understand the champion they are playing and equips their champion with items that help them play to their enemies weaknesses or exploits the enemies strengths.

For example, I can't count the number of times I've heard an adc say we need to focus soraka because they think she is OP. Sure Soraka can just keep refreshing her allies and be annoying to lane against, but if the adc would not rush the typical starting item of a BF sword or atk speed boots and instead rushes the cheap item Executioner's Calling, Soraka becomes mostly negated along with the sustain and lifesteal of other enemies when the adc focuses them. Sure it doesn't have the impact of a BF sword, but I find it to be extremely useful to starve opponents out of lane. This gives a great gold advantage in the long term.

This is just one example of counterbuilding or building for the match. I feel Riot should have an item effects/ passive tutorial in the game or client that allows players to explore the possible effects of these items without having to be in matches or customs. Thoughts?