Because the games that deserved actual backlash (to the extent that the legal system became directly involved) was relevant to the product itself. I noted this earlier in this thread, but A:CM was a different and clearly substandard game at its core compared to the demo. Nearly everything about what made the demo appealing did not make it to the final product. The demo showed Xenomorph AI actually react to the situation, instead of blindly charging forward. It showed great level experience that weren't in the game and graphic quality that stood above and beyond expectation. Add to that Randy Pitchford's false commentary through interviews and making-of promotions that used the demo, rather than anything akin to the final. Everything that would make a modern game appealing. Sadly, they even went to the extent of hiding the fact they outsourced nearly all of the game, despite claims through those interviews/promotions that they were implying it was developed in-house.
The situation here is absolutely nothing like that. What we have here is the equivalent of a gun in Halo not functioning exactly as we'd see in a demo. That's all. That's why the devs here get a pass. People making comparisons between those games and what is happening here is ridiculous and evident of folks who are 1) making a big deal out of what is essentially nothing and 2) failing at understanding the situation. Part of said failure being their lack of remembering that this is an MMORPG. Nearly everything about the gameplay (besides the genre itself) is subject to change for better or worse.
Edit: For clarification, my mention of "nothing" there is referring to severity, rather than discontent. Express concern and all that, but people should learn to not treat it like some kind of crime against humanity. This game, like many others in the MMORPG genre, are known to adjust things or make changes... in case anyone forgot.