Why isn't that the point of this question? Yes Rainbow Crystal Staff is kind of bad and also doesn't feel like it fits in with the other Moonlord drops. I do like the Lunar portal staff It just seems strange for Moonlord to have two sentries since without OOA equipment you can only have or use one. Personally as of 1.4 the most boring weapon is the SDMG. Meowmere can't be called weak due to its high damage and like
Derpling Ω said the trait you are dissing is actually an advantage of the weapon which increases its potency even more.