I think age factors into it. Waaay back when, the first split in the Aliens fandom came in 1991 with A3 killing the established direction J. Cameron was seemingly taking the franchise in. I remember feeling pretty let down that everything I thought was "cool" about the franchise (the space marines, the guns, the heroic male characters) had been erased and replaced by just Ripley's hellish isolation tragedy opera.
A:CM aimed to fill that hole by offering an alternative sequel than A3 was. Opinion on how it played may have been divided (though the Templar GfX mod changes the gameplay completely), but personally I loved the script as it put me straight back in 1987-89 with the sequel to Aliens we should have had.
I can imagine that people like me love it for the overall 80's plot. But if I was a kid used to modern, polished, call of duty, Battlefield type games which are genuinely FUN to play, and not having lived through the backstory of the 80's, I would probably not care much for A:CM.
Had A:CM been a lot more polished with much better gameplay, and gotten more traction, I think the franchise would have been a lot more of that dark 80's corporate scheming, Earthbound, don't know who you can trust, corporate types screwing each other over for a dollar, with Xenomorphs running around (like the awesome comics really).
For sure we wouldn't have had the current idiocy that an angry android CREATED the xenomorph in a bout of narscissism and fit of mental masturbation.