I wouldn't call it vanity; it's too harsh and unfair. It paints people who are enthusiastic about their accomplishments in a negative light. People shouldn't be ashamed to be proud of their honest work.
Showcasing isn't essential, but it can increase the enjoyment and it can benefit the others. That's why we have art galleries, trade fairs, talent shows, and Show HN threads.
I specifically asked about how "They need sincere search engines, that's all." What exactly content creators should do about it? Make their own, sacrificing time from their main hobby? Maybe one already exists. But then they need to tell their potential fans about it. How would they contact them? They might not even be aware they exist. I guess they could wait until the new sincere search engine reaches critical mass. But what until then?
As for the "wide audience", consider this. At one point in their lives, fans were part of the wide audience. They weren't born fans; they became them over time. So why shouldn't the content creators try to capture new fans from the larger audience? They don't have to - becoming too mainstream is a thing after all. But if they choose to do so, why not? Unless you oppose the creators growing their fans and popularity, in which case I don't know what to say.
