No you can't. Overwatch, CSGO, etc, etc. don't have a way to make a team and queue as a team (against other teams). You do this by playing on FaceIT, ESEA, CEVO, or in other leagues. Built-in matchmaking is only individual. This is, from a competitive standpoint, a meaningless data point and (from a casual standpoint) only creates toxicity.
I don't think this is true. I play Overwatch and I sometimes play with anywhere between 1 and 5 other players as we have arranged to group up before looking for a game. With 5 other players, it's a 6-stack, and I believe that a 6-stack will always be matched against another 6-stack. As far as I know, it takes the average skill rating of your group and finds another group with a similar average skill rating to play against you.
I do miss the old days of CS with "clans" where it wasnt so hard to join up and have a lose group of people you played with regularly and got to know ~20-30 people and whoever was on would join up to play together (maybe this still exists, but I havent found it..)
That's exactly the problem. The MMR system isn't based off of team ratings, but off of players. Otherwise, teams (e.g. 5 players) would always play against other teams (another 5 players). Now, even ignoring the model problems this generates (and the gymnastics that something like TruSkill does to mitigate it), it's just a bad experience.
For example, if I go to the beach and join some random volleyball pick-up-game, I'm expecting that the purpose of the game is to "have fun." If I'm joining a team to play in a rec league, the expectation is to try and win. The idea of "matchmaking" mixes these two concepts, so you end up having different people with different expectations. Some are going to say "why are you trying so hard" while others will retort "why aren't you trying harder?" This misalignment of expectation is, imo, the chief cause of toxicity in (competitive) video games these days.
