Usually a newcomer is invited to join Nostr, even if only indirectly by reading an article or watching a video or talk. For the few who start from scratch, clients usually suggest a few people to follow or automatically follow the developer. Basically you always have someone to build wot.

But the point here is that without a sensible filter newcomers get confused, and runs away. The only alternative I can see is a single relay with good spam filters bundled in a client; but it's not very Nostr style.