The Red Star was broken. No beings were resurrected and teleported back, so from the perspective of those inside the robot death was permanent. That's why conflict and wars, assassinations, etc, developed normally inside the giant robot.
Also, the population did not remain consistent on its own, because nobody came back. As such, new beings were created.
Except that we don't know when it was broken. The only hint we have regarding that is Greg F's statement that it was "broken a long time before the events of Mystery of Metru Nui" That could mean anything from 10000 years to 100000 years ago, and unless we know that it was broken almost immediately after the creation of the Matoran Universe, it means that for some period of time the MU did experience resurection. Which leads me to the biggest question of all: if the Red Star didn't break almost immedately after the MU's creation, then how come Helryx and anyone else from its early history don't remember that beings were being resurected?
First, there's the consideration that Matoran weren't sapient for the whole time that they were in the robot, and might not have noticed.
Second, there was enough of a hint in the whole Gaardus thing to place the breaking of the star far in past - 80,000 years is a BS01 approximation.
Third, even if those early people did remember, they would also notice that it doesn't work now. They wouldn't know why the beings in question aren't being resurrected - probably come up with some cryptic thing about destiny to explain it in their heads. And why would they tell the beings who don't remember that beings were resurrected at one point? That will just make everyone think that everyone who died is evil. Why give out what appears to be false hope?
If it's any comfort, I think based on the criteria for resurrection, around 3/4 of the named characters who have died in the story are still dead; they were never resurrected. The remaining 1/4 are still mostly unconfirmed by name. Moreso, the Kestora killed a lot of resurrected beings, so it's possible pretty much the majority of people who have died over the years in the MU are permanently dead.
I've had time to consider the twist, and while I don't think it's BIONICLE's best twist, it's most certainly not the worst twist in any work of fiction. I don't mind it much, but I am still very irked regarding Lhikan. I still hope, although at this point it's very unlikely, that maybe Lhikan is still dead somehow.
I can't recall a case where Greg F. confirmed something about the story when the exact opposite was true. He's long had the exact opposite problem of many writers: instead of flat out lying when people ask him about plot twists, he's all too willing to spoil the details. Now that the story almost certainly will not continue, this probably is even more true - so I don't have my hopes up. What ir me even more than Lhikan's death being retconned, however, is that so many people seem to be genuinely excited about it. How can this be exciting when it means that all the emotion underpinning his sacrifice is cheapened in the process? If people are so eager to see him give advice to the Toa Mahri or whatever, then they should write fanfiction. If the official story somehow manages to come back, then why shouldn't it focus on the 17 zillion canon characters that are currently living on Bara Magna, instead of devoting time to formerly dead Turaga whose character arcs were already concluded satisfactorily over half a decade ago?
But this isn't Bionicle's eventual return. It's just an interim story in between the story we know and a possible return.
X-Ray 
