Any specifics on why it's being received so negatively? 
well if you ask , you see the reason i discovery Japanese complaint and bashing about ML begin on the day ML launched, i curious how Japanese fandom reception on ML i think is going more positive than i thought but hoo boy how wrong i am, i think it just on one website so i check several other website boy i am wrong again.
and now i present you the Japanese fandom complaining and bashing factor on ml:
warning:please prepare your mentality and your faith on im@s fandom
1.the fact ML using anime artwork:
surprise surprise the Japanese fandom dislike the fact ml using anime and accusing scamco being to lazy and some say their miss im@s old style artwork heck there even say they are crappy and of course there some (more many though) cg artwork is superior.
2.ML character
since first day (yeah i checked it) the Japanese fandom reception toward them is negative.
here the most common bashing:
their face same, clone, rip-off, not original, no individuality,their hair is unrealistic (to some of them)
and somehow the bashing getting worse (in some side) after ML release some comment call them don't have im@s character aura or simply don't feel there a new character
some community dislike the exclusive privilege ML girl get (voice and album)
and don't bought up the fact ml girl is part 765pro a good way you getting bashed here a excellent comment from them:
"i can't not laugh with fact them (ml girl) is part of 765pro"
"how can be they are part of 765pro"
heck there are who skeptical 765pro main girl going be shoved out and ML girls is the main focused and with the fact i mentioned earlier well....
3.ML concept
one of the plus point the Japanese fandom negative reception toward ML
here a rough ML concept:
a group of idols (in ML case 50) sing in place called theater remind you with something?
yeah the fact ML make 765pro being like AKB is make Japanese fans rather unpleasant at least
and here the comment which work as last strike to me as this comment make me look ML jaded and skeptical as now:
"765pro in regression/is degrading" (i forget which one is true probably because i don't wanna remember it)
as above comment say many Japanese fans think ML concept make 765pro lose it way or lose it originality.
4.the complaint (which probably the root of most current bashing)
many complaining the fact ml have many bug, error and technical difficult.
well that's it the reason why Japanese fandom bash and complaining ML it doesn't help some Japanese fans maybe dislike ML as ML album pre order starting to drop (this or the fact ML album published by lantis) however there still some who like ML even it's not much as the hater so don't worry
also one last thing there one thing Japanese im@s fandom really want a genuine sequel, a sequel with im@s signature game-play.