If someone just doesn't have the gear

If someone just doesn't have the gear to contribute as much as everyone else in the group, they're either getting carried and/or helped, and the difference is in the group leadership. Someone who just sucks even though they have the gear is being carried, no question, and should be kicked unless the group feels like carrying them or decides to start helping them.
euwowgold.fr
There is no bulletproof way of knowing if a stranger is going to be terrible. That's why I always invite a few extra people to my flexes so that I can kick any baddies I come across with minimal fuss and record their names so that I don't invite them again. That's why flex is so great, you never have to really commit to a player you don't know.

New players can get sponsored the way I did when I started and the way I sponsor players now: Join a good guild.