With no blacklisting available it doesn't take much to overwhelm the gallery with a single type of content. Heck, posting batches of ~6 images every single day can already be annoying if you post low quality content. The one thing that keeps the gallery legible is the relative low total upload rate of about 8 pages a day. Can you imagine browsing through a more busy site like e.g. Derpibooru with no filters?

Spamming on KYM is fortunately not very prominent because it's not very rewarding. If an image gets few upvotes it won't trend and not many people will see it. And most users just ignore those or report the poster so he/she leaves or gets warned/banned.

Still, because it's so easy to upset the equilibrium of this ecosystem, people are constantly complaining about seeing too much animu/controversies/lewds/cringe/normie content/Trump/etc.

We're still waiting on an Edit Comment feature; wouldn't hold your breath.