I was wondering, what is Warzone's active player base? I've had trouble filling even 7 player games, sometimes it takes up to 2-6hr to fill up a game of such small size, and it got me wondering about this question.
Hard to say without behind the scenes numbers, at least AFAIK. I had the same feeling when I came back.
Generally speaking, QuickMatch sucked a lot of life out of the RealTime lobby. Games also fill up a lot faster if the settings are more casual friendly/mainstream. So it really depends what type of games you are making.
Real-time open games ain't what it used to be sadly (especially if you're trying to play on anything other than Rise of Rome, Small Earth, or Imperium Romanium). I think majority of the player base moved to QM.
There are 87 000 players in Quickmatch. If I am correct, QM was introduced in 2017 October and first month had 20 000 players ranked, next few months doubled it quite fast. So take 40 000 players got ranked for years of 2018 and 2019 - so its roughly 1500-3000 players per month. For previous years its around 13 000 accounts creations a month. If 2019 ends I will check how it changed for this year.
There are different levels of activity. Some play only single-player, some occasionally real-time, up to players who visit at most every 3-days and are considered the most active in Warzone. My own estimate is that, there are no more than 20 000 very active players (excluding players who are new). But there could be up to 100 000 individual account visits to the site.
To be fair, even before QM 90% of RT games were Small Earth dumbness, ROR, Imperium Romanum and failed diplos/huge FFAs that never filled. I rarely ever check what's happenig in MD open games so I don't know what to say about it.