Well, the complaint about listening to others...if you cannot work out how to mute a player which takes all of 2 seconds I don't know what to tell you.  Is a completely redundant complaint.

3DS doesn't really do anything right, why would you only want to listen to those you added?  Are you anti-social and incapable making friends?  Aside from a few people you may need mute there are plenty of decent people out there on PSN and XBL who even if not on your friends list can be nice to chat with during a game, even make friends of them.  Sadly friend codes offer none of this, may as well be playing against bots. 

Adding people is not the same either, on PSN and XBL you can send a friend request either by typing a gamertag or selecting it from a 'recently met' list, you can send a personal message with the request and all the person who recieves it needs do is accept the friend request.  On 3DS if you want to be friends with someone the first thing you need do is remove the 3DS from the equation because it is useless, you instead need go to a forum or something and exhange friend codes there, then both add eachother.  On 360/PSN if someone for whatever reason denies a friend request the sender immediatly knows, where as on 3DS that pending request will sit on your friend list forever if the person does add you until you finally realise they not gonna add you back.

SO there you go.

Hopefully, yes.

Are you one of those people who believes people listen to you when you call out tactics?

Wii has codes for every game.

3DS has a unified friend code that covers all games, and an actual functioning friends list, and the option (if you're in the same room) of friending someone without actually exchanging friend codes.

If they progress in that direction, it's likely that friend codes will be a primarily background thing unless you set your parental controls that way; with luck, you can just add people by their username, like the Nintendo Direct video sort of hinted at.