its a mindset.
firstly, understand that people at those levels are expected to be bad. If you expect them to be bad, you'll get less angry when they perform at your expectations.
Secondly this game has a tonne of elements in it. champs, items, masteries, runes, spells. People are learning at those levels so give them a break.
You can teach them, but it is hard for them to absorb it during the heat of the moment. They may not even know what CSing or warding means. You can kindly suggest thing to them, but don't expect them to follow.
There was this one game where the enemy team does alot of magic dmg, and I am begging our support to buy aegis. After 5mins of begging, he snaps at me and goes "WHAT IS AN AEGIS?!?!". I tell him to look it up in the store. 5 mins later, he still doesn't have an aegis. He still didn't search for it. Reason? He didn't know that the shop had a search function. So I had to tell him null magic mantle + crystalline bracer. This was a B2 ranked match.
That match surely was an eye opener.