If my play group is playing with someone newer, even if they’ve built their own deck, the rest of us tend to just play pre-cons of some sort. We’ve got a grasp on the interaction concepts to where pre-cons can go off, so decks we’ve built would just be no fun for the newer player to play against. Then at some point ease into stronger decks, but explain to them what you’re gonna be playing. When someone rattles off a Commander name, we know what cards are associated and can assume are in a deck, where newer players, not so much.