There sorta is a matchmaking for raid and nightfalls not sure about levithan raid but I know for last wish SotP and the new one there's a "beta" option to can pick you can either go in solo and get matched with a full team or go I with 3 team members and paired with 3 others. You can even go in with 5 and pick up a person whos searching as well. It's not efficient but I think it's the best we're gonna get same goes for nightfall