Okay, yes but that's what I'm saying. Moira isn't creating splinter timelines, her consciousness simply hops to a parallel (very similar) one. There's actually no "new creation" then and it honestly gels better with current editorial fiat.
there is no parallel (very similar) one, because the universes that exist in marvel were created by Franklin and all distinct from each other. Many of these were destroyed by the Entropy Abstract in Fantastic Four earlier this year. There are not an indefinite number of Earths all identical up to the point of Moira's conception.
There is exactly one, and it's timeline is being reset.
This idea that Moira reincarnates and resets the timeline really just doesn't work within the framework of the multiverse either; because there's countless Moiras and the notion they're each constantly resetting their realities really just is sort of untenable. Maybe if our Moira is "unique" it becomes simpler to rationalize but constant continued timeline annihilation across the multiverse with a near infinite Moiras is something that larger powers would've taken notice of well before now.
I'm not sure why you're struggling with this concept so much. There is one universe at play here, with Moira's conciousness time traveling back to her conception every time she's killed, resetting the timeline. One Moira, One Earth, one timeline that's annihilated when she "resets" events. Alternate universes are unaffected because there are no Moiras there.
The larger powers don't care what happens to a single universe unless that event is catastrophic, because there are (or were) millions of universes out there.
and once again, the marvel multiverse as it exists is not infinite. It is composed of a finite amount of distinct universes Franklin made, many of which were obliterated in the current run of Fantastic Four.
edit: you're also overlooking that if the timeline of life-6 isn't annihilated, then the Dominion (which exists outside of space-time) would have destroyed Moira as it would have considered her existence intolerable. The fact that it has not means that it is not a parallel timeline, but a potential future that was invalidated at the moment of her death and reincarnation.