This is one of the reasons projects take that long to index in the search engine.
Itch.io is focusing on allowing indie devs to publish their content as easy as possible. This has its drawbacks, but it’s one of the reasons new accounts with new projects go through a review to check on this activity.
What you are describing is not unique to Itch.io, users can for example post pictures on social media that break the rules there. The picture will appear instantly, but soon after it will be taken down.
The alternative is to have stricter controls on who can make accounts and publish content, maybe even ask users to pay to publish, which honestly I think will make Itch.io lose part of its charm as an indie friendly platform. Of course every person has their own opinion :)