I'm sorry, can we appreciate these models??? those are fantastic!
However, regarding the discussion of whether or not a Sanrio / Hello Kitty crate is "popular", this could be argued for every single franchise/idea. It comes down to preference and opinion. Everyone is entitled to their own opinion - if a crate is produced and you do not like the theme, you simply do not have to buy keys for the crate. No one is forcing you to buy every single crate, they are optional, so it is entirely valid for people to suggest concepts that may not be seemingly "as popular" - If you have no interest in a particular franchise, of course it will appear to be not as popular as you do not expose yourself to the content/media.
The ManaCube community is so widely unique, that there will be players who will appreciate the "niche" themes for crates, and if you are unfamiliar with a theme, it may introduce players to that concept and they may enjoy it. For example, there may be a young player out there that has never really been exposed to Hello Kitty, but if this crate was made, they may see it and really enjoy it! I think the issue here seems to be that the crate idea suggested is portrayed as more "feminine" and "childlike" which there is no issue with, but I can't help but feel that is the root of the disagreement towards it. A large portion of the crate ideas seem to be targeted towards "masculine" themes: Marvel, Pokemon, Skyrim, Medieval, etc. Now, as someone who is a major fan of the latter 3 crates mentioned, I can admit that there is a bit of a masculine undertone. Of course, I may be wrong in this assumption, but it is certainly a possibility that could be considered also.
With crates like SpongeBob, Pokemon, Marvel, etc. I feel like the addition of a Sanrio crate would be purely nostalgic for a large group of players. Of course, it won't be everyone's cup of tea so to speak, but it is so unbelievably difficult to create a crate idea that 100% of the playerbase will like. Regardless if a concept is popular or not, it doesn't mean it is for everyone! I think it's important to consider personal bias when reading others' suggestions.
(P.S: We even had an entire crate dedicated to fruit because of player suggestions! hahaha)