If it weren't, then every review of every play and show and movie and novel would have to avoid any remarks on the characterizations because "what does it matter, they're only two-dimensional and we shouldn't expect anything of them."
You're straying off the subject a bit. I'm talking about the criticism of the characterizations of the sequel, NOT the original musical. The acceptance and embracing of the paper-thin characters with little-to-no back stories, but the rejection of the change of the characters from a ten-year gap in the story as inconsistent and/or unrealistic. The problem is the level of expectation on the sequel based on the level of acceptance of the former, which seems contradictory to me. The ten-year gap and the application of realistic human changes of behavior seem to be the offenses. That's what I find so humorous.
But it's perfectly legitimate to want fictional characters to have a little consistency and integrity.
Okay, and you get a little, which is proportionate to the depth of the characters of POTO, actually. The problem seems to be the idea of these characters being depicted as realistic people who change decade over decade, rather than exist in the less realistic bubble of the consistency and integrity of...what? Is it preferable to simply repeat the gothic cartoon of the original? Raoul is a guy who knew Christine when they were children, happens to attend a performance, falls in love with Christine and generally hangs around. Ten years later, we find out that being a guy who loves Christine and hangs around as an ineffectual hero isn't all there is to him. And Meg! What is her consistency and integrity? She's Raoul without the romance. Just benign observations and occasional fear.
You really seem to have no high regard for either the original Phantom or this musical, but keep coming back to make fun of people for... actually caring about stuff.
Oh, dear Lord. Spare me the exaggerated melodrama (POTO and LND have more than enough). I enjoy both shows to varying degrees and have spoken about them often. I've seen POTO about half a dozen times and have seen both this tour and the original London production of LND (and watched the Australian video). I don't "spend hundreds of dollars" on something for which I have "no high regard". I spent far less than that for LND recently, in fact. I'm being objective with respect to criticism of the treatment of the characterization of LND when compared to POTO , as well as being objective with respect to the books of both musicals. However much anyone cares about POTO alone is fine and their level of obsession with it is their own thing. But if you're whining about "character assassinations" of LND (of which there really are none), then you really seem to not care about the latter and may be spending hundreds of dollars on it, anyway.
It could have worked as a separate show entirely - but the use of the characters of Phantom and make them behave implausibly, with equally implausible events is ridiculous.
They've always behaved implausibly in implausible events!
The problem seems to be that the characters are not shallow enough and that LND is not a more direct and continuous retread of POTO.
Even if the characterizations/plot hole were ironed out, it still has the fundamental problem of trying to turn an unrequited love story into a requited one
I agree that this is probably the heart of the issue and the catalyst to the plot is based on events that occurred between the two stories rather than on stage. The kiss between Christine and the Phantom (to the melodramatic disgust of Raoul!) seems to be the inspiration for the catalyst, but the way they attempt to bridge the gap is clumsily written and structured.
or else risking being a redundant re-run of the original plot in a much more pedestrian, soap opera fashion without any grand guignol.
The grand guignol is the only thing that keeps the original plot from being a pedestrian soap opera. Take away that gothic horror and you've got a very thin very redundant melodrama at its core. The grand guignol was then replaced with the gothic horror of the freak shows of the early 20th century and much of the score and story are intentionally structured to mirror the original. I'm not a huge fan of the story for LND, but then, I was never a huge fan of the original story, either. To me, what sets them apart are the staging and the scores. POTO is far superior in both.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian
That's a given. But it's perfectly legitimate to want fictional characters to have a little consistency and integrity. That isn't a new concept; it's one of the rules of good storytelling. If it weren't, then every review of every play and show and movie and novel would have to avoid any remarks on the characterizations because "what does it matter, they're only two-dimensional and we shouldn't expect anything of them." 
