This is a very standard Trek episode - nothing particularly interesting is advanced for our consumption, but there's nothing structurally wrong with it either. In point of fact, the way they did this Voyager in multiple dimensions plot was better than the way they did the other two similar plots that they'd attempt later in the franchise. It's just that this particular story idea doesn't have a ton of upward mobility - there's nowhere for you to really go that would have made it a better show, with one possible exception.
They kept us in the "oh shit!" universe for a while before revealing the "other Voyager" that was just fine...but they should have kept us in it much longer. hell, have the "oh shit" Voyager be the one boarded by the Vidians while we're still trying to figure out what the hell is going on and have us make the choice to self-destruct Voyager without even knowing that there's an alternate ship that will survive...and then make the big reveal, after we see Voyager blown to kingdom come. We should see Vidians killing as many of the regular crew as possible before the self-destruct is issued - they should be fighting for their lives right to the bitter end before Janeway decide to give us the "Janeway Pie" ending. The mystery is the only thing keeping up the suspense - as soon as we know there are two Voyagers we know how it's going to end and we know everything will be OK. So keep us guessing as long as possible. That's all you can really do to make this idea work.
2:22 - Innocence - Overall Rating: 5.0
Boring + implausible = crap, but not INSULTING crap. Let's try to fix both problems (the boring and the implausible) as much as possible. First, I'll tackle the implausible part. How, biologically, would it possible work that a race ages in reverse and then dies as a healthy child? How would their mass reduce? How would they reproduce? How would their minds become confused? They made no attempt to explain, which is better than their usual illogical attempts, but in this case, I can think of only one possibility. They reproduce by having mastered the matter/energy barrier - they extract energy from the universe and use it to create whole people fully grown, but their energy is not stable and they do not last forever. As their bodies begin to lose energy, they necessarily shrink and they start to lose the ability to hold onto memories. Their final death is a dispersion process and needs to take place at the sacred planet in order for the energy to return and be recycled by the machine (which we could find at the end of the episode). Even the ionic turbulence could be explained as the unique energy needed to power the machine - the remains of the dead who will become the living. This sort of thing actually does need to be explained or it all just feels fake and forced.
As for the boring part, we should have seen what we thought was the Morrok - and we should have seen it "eat" the children one at a time...when what it actually was was the atmospheric disturbance caused by their energy matrix destabilizing and them dispersing. That would have created some sense of jeopardy on the surface. Meanwhile, the Tarkannans that Voyager was dealing with should have been perhaps a little more imposing. We weren't ever really threatened by them...they just got cranky and we did what we wanted to anyway. I would submit that they should have been a more formidable adversary...and that when we outmaneuvered them to reach the planet and discovered what was really happening, we'd have to talk them down (with the help of Tuvok, who did, after all, play the critical role of guide for the dying). I mean...otherwise, the tense music and such all seems a little silly. I know, I know...I'm reaching here. This episode was just dull as a five hundred year old knife.