Well, Elitist it is not picking people on the same rating and play with them, its really ok, Elitist is it when you play with people with your level and still doing those lines "Lul, could tank better, lul i would heal better, lul what a noob route and stuff".
Its clearly understandable why you pick people around your playrating/clearrating, as a pug-player I'd join raid with curves when have curve. And I totally understand why people decline some people that want to join and dont have one. Sometimes people give chances and we use them to get achivs and right M+ clears, but it happens too rarely.
There are some people who're instantly hostile to new people, there are opposites. And I totally understand both sides.
My point is: One thing that makes you a truly mister elitist -- hostility towards another players. Not the way you pick the players. But thats my opinion
It's not a bad thing that you dont wanna spend your free time on freeloaders or lowrio players. Well, I guess thats how life sometimes works (It's really becomes clear when you split up with your friends in RL. Sometimes people even stop to hook with other people jsut because they jump up on higher levels, speak with much wealthier people and dont wanna waster their time on people who's on lower level.)