Why are the pub lobbies so sweaty?

Is there some sort of skill based matchmaking that’s tuned up to 1000? I have 700 kills with my main and I’m running into people with 3-20,000k kills IN PUBS!!! I’m not even the max level (lvl 70  right now) and Yet everyone I encounter is max level. Does it have to do with KD? Why can’t there be a system where it puts you in lobbies based off your level, wins and overall kills