What is normal. Its decentralized, permissionless, but you can set filters for content the way you like it, or just ignore it, we can't really "stop it".

It’s best to block/mute as many of those tags as possible, if you don’t wish to see that, Nostr is content agnostic. 🙏💚

Some relays also block NSFW content fully, that may be the safest option for you.

I report anything nsfw with any mention of children… which that does, Jesus. 😰