We all know that screaming at a teammate for "being bad" etc. doesn't work; no one responds well to that and it's rude. Constructive, courteous criticism is encouraged: for example, telling someone about a new way they can use an ability, like using Aatrox's E during a Q cast, or recommending a specific item, like Adaptive Helm when facing a DoT champion.
But... have you tried doing that? Does the person receiving your friendly and respectful advice actually listen to you? Lately I've noticed that it doesn't seem to work, mostly when encountering people who stick to recommended items with no thought to strategy, viz, stacking armor when the enemy team is literally five mages. When I see what these people build, I try to give my advice in a casual, offhand manner calculated to spark the least possible ire. "btw, you could sell those tabi and buy merc's; they have 5 mages with heavy cc." I get literally no response. No "I don't believe you," no "I don't understand," no "gtfo i h8 u," nothing. It's like I'm not even there.
Polite, constructive criticism is better than flame with no actionable advice, but is "better" enough? Is it actually effective?