1: Its not that they refuse to get better, its that they don't know that they are not doing it right. They don't look up how to play their class because as far as they can tell they are doing it right. Most people you meet will ask you a question rather than using the phone in their pocket to google it themselves, they don't ask you because it is easier (they probably asked 4 people before you.) but because their brains don't pull up the fact they have the worlds repository for information right in their pockets.
2: Most people think that saying, "LOL L2P! REROLL!! LOL U SUK!" to someone who is underperforming is 'helping' them, or kicking them from a group for low numbers is 'helping them'. They may not be elitist assholes but they certainly are assholes. Very few players are the type that actually try to help another player. Another trick is approaching a player who could use improvement and not upsetting them, its natural human instinct to reject the ideal you are doing something wrong. You can't tell them "You know your dps is bad, use this talent and this ability' without them rejecting you. I tend to say, "Lets try something out, if you don't like it you can set it back easily, try this talent and see if you notice a big difference." then I suggest noxxic.com to them, as its a more basic 'wow for dummies' website. Most underperforming players have had such badly delivered 'criticisms' that they just chock it all up to assholes, thats not the underperforming players fault, thats the assholes.