I think that there should be an external website or an in game way to post maps that you create so everyone can use them and there should also be a way to download maps other people created and posted.
There is already a way to share your maps. I implemented it with the GameJolt API, meaning I use their website to store maps online, that is why I don't let everyone upload. Only users with a GameJolt account can upload and share their maps to avoid spam. If you have a better way to remove annoying maps please tell me and I will consider it, until then an account is required for logging in before you can upload them.