I’ve been playing Halo Reach online multiplayer and there are hardly any players left. I’m unable to play certain game modes and if there are enough players, it takes about 15 minutes to find them. There is vary bad lagging, which is almost constant. I think that the servers are just not maintained as well as they were before or there are so few players that the servers are having trouble connecting players.
It depends on what time you are playing. I live in the UK, and whenever it hits nighttime for me, I normally see just under 3000 players online and can connect to them fairly quickly; but as you said, some playlists don’t even have a population, so I just end up playing Infection.
I live the South East United States and I usually see about 1,300 players online.