It is considered a "derivative work" rather than a faithful encode of the original source. Is Moozzi2 right for you?
This is the purist's biggest gripe. The studio colorists and directors chose those specific muted colors and that specific level of grain for a reason (atmosphere, mood, time period). Moozzi2 ignores all of that to chase "pop."
If you are archiving anime for posterity, skip Moozzi2. But if you want to watch Highschool of the Dead or Log Horizon on a Tuesday night and just want the colors to blast your eyeballs off? Grab the Moozzi2 release. You’ll have a good time.
Moozzi2 almost always thickens and darkens the line art. In original BDs, lines can be thin, grey, or broken due to compression. Moozzi2 makes them solid black.