The concern about Marathon's playercount stems from the experience of D2 Crucible players, where reduced numbers could severely affect queue times, lagginess of eventual opponents, getting matched against the same teams over and over again in Trials, etc.
Yeah. From historical precedent (basically every other live-service FPS game in the past ten years, when they all started leaning heavily into "matchmaking" with endless behind-the-scenes voodoo to screw with everybody's K/D or W/L or whatever to force everybody into supposedly "even" matches), it seems like there's a bare-minimum number of active simultaneous players in a given game before its matchmaking system starts to break down, and it's a surprisingly
high number. Low five-digits. I haven't pinned down the precise range where such systems start to fall apart, but it's pretty obvious they need at least 10k+ active players with different "qualifiers" or "metrics."
There's weird misbehavior that starts at that level of available players. Rules fighting other rules, some more heavily weighted than others (which makes sense), but with conflicting "overrides" that result in the worst possible outcome: potentially hundreds or even thousands of players, all readied-up and no technical hurdles preventing their playing together, but the "matchmaker service" says they can't play together because "reasons" so they have to sit in queue staring at "500+ players in queue" instead of playing together in a potential "skill mismatch."
The worst part is these companies have spent two decades developing their matchmaking stuff and it's all evolved towards this "everybody deserves balanced, fair play at all times no matter what" mentality (because fuck your skills and practice -- if you're doing too well, we'll intentionally set you up with our "best" players so you'll be roflstomped back down to know your place), and by god they're going to stick to what they've made no matter what feedback they get. And the dumb fucks ignore obvious fixes that are "better than nothing" because they fear the fixes aren't 100% perfect.
Namely, if you've got a game that's running 3v3 or 5v5 fights, if you
ever have six (or ten) players in the same geographic region queued up for a new match for longer than one minute and they keep getting "rejected" by the matchmaker system for whatever reason,
just fucking shove them in a match anyway. Randomize the teams, fuck "matchmaking," just spin up a session and shove 'em in. Get them
playing. I guarantee they'll be happier playing a less-than-perfectly-matched game for 10-15 minutes than sitting in a fucking queue for 20-30 minutes staring at a spinning indicator.
But they won't fucking do it. They'd rather make people sit and
not play rather than risk "making" them play an algorithmically sub-optimal match.
Low player counts exacerbate this. You don't see it when you've got an available pool of thousands of players just queuing up for a match at any given moment. But when you're down to "just" 10k or so, your super-choosy, super-clever matchmaking algorithms fall apart because there's always a nit-picky reason to exclude X hundred potential matches each time you check.