You play on xbox which has a stupid simple lfg system built into the os. If you don't like who you get just kick them and re post in the lfg. They don't put matchmaking on end game activities because there needs to be a bit of personal refinement to the fireteam you go in with. If it was there you could easily expect the kind of people you get in heroics or normal strikes. Little to no comms, afk, reckless, etc. It would make things worse honestly because there have been some heroics I've where I only have one other person in my fireteam and we pick up a random and the random either does nothing or is just dying constantly taking up space and adding health to the enemies. At that point it would be easier with just two. That's not even talking about challenge of elders. Most people just want to burn through the bosses while some want the score for the drops. Having those groups be thrown together would be disastrous.