The live service had a pretty bad year last year. The linked article goes into great detail but I think it can be summarized in a few points:

• The game shipped without campaign co-op or Forge mode. Forge in particular was a big part of the longevity of prior versions of Halo, and having that missing did them no favours.
• There was a battle pass, but it had a rough landing. Players couldn’t select the map they wanted, so for some battle pass objectives you had to rely on random matchmaking to achieve your battle pass goals.
• There was a pretty serious content drought last year. Relatively few new maps were added by Infinite, compared to content release timelines for prior Halo titles, and users couldn’t build their own maps because Forge was still missing. 343 originally estimated 6 months to finish Forge, but it actually took a year. They had to keep extending the “season” for the aforementioned battle pass, likely because they didn’t have the next round of content ready when they expected.

I think the content drought was the biggest problem. With only a relative trickle of new content from 343 and absolutely zero community content (because that would have required Forge), there wasn’t enough to retain player interest.

I still play it with friends every couple weeks. We still have a good time, especially now that you can queue FFA with friends, and now that there’s infection. Being able to play against each other adds so much to the experience.

I think the struggle just comes down to how little there was at launch. There was no progression system (the only way to earn anything was to do chores), there weren’t many maps and modes (launching without forge really screen this over), and there was no PvE you could do with friends.

If the game had launched how it is now (so, 2 more years of delay which is insane) I think it wouldn’t have died off as quickly. There’s actual XP now just for playing, there are a lot of maps and modes and a community maps playlist, and campaign co-op.

tl;dr same as what everyone else always says. 343 dropped the ball hard on content at launch.

I used to play it regularly with a friend of mine, even until they finally brought co-op.

The main problem with multiplayer as of now is that it’s gotten boring. The only new things they keep bringing are overpriced cosmetics (which aren’t even that customisable) and network bugs that break gameplay. There are no new maps and Forge seems to be dead on arrival.

Also, this game feels strangely unoptimized for what it is. Its graphics and level detail don’t justify the amount of hardware resources it eats up. And it has only gotten more demanding over time.

My girlfriend and I dipped out after MANY months of BTB being completely non functional. The 4 player Playlist got stale as all fuck (due to having like 3 game modes, not even infection until this sesson) and we just haven’t been back since. We play MCC now and again, but infinite really screwed the pooch on this one.

I’m not opposed to ever booting it up again, it’s just gonna have a very hard time competing for our time