One big issue is that everyone knows its an issue, so people add more places to store information, which inevitably becomes another place to search which makes it hidden, and then as things move there are inevitable dead links all over the place. We need an intranet to be an actual intranet with all information there, and properly indexed.
The biggest "solutions" here are also some of the worst offenders:
1. Google Drive / Microsoft Network Share / Drop Box Etc. These are filled with documents, some companies have more than one of these. These are places where information goes to die, and lives entirely in people's heads, so you have to talk to someone, have them find it, send you a link etc. If there is a search, its for the names and not the content. They are rarely in a good format or place to easily do a find | grep search.
2. Confluence is awful. Confluence is directly backwards, its information at the team level, instead of at the topic level.
3. Sharepoint purely awful. Its searched poorly, barely works.
4. Wikis, very few places uses these for some reason in favor of worse. A single source of truth wiki I think is the optimal place. Or if they do its like a MS Team Wiki or a Gitlab wiki that is broken off of all other places and not indexed so its disconnected.
But the truly loved search service within Google is codesearch. And that's great
It would make sense as it would be in the company's best interest that the employees be shown meaningful results when they're trying to solve problems. A completely different index/ranking algorithm that punishes, instead of rewarding, all the fake SEO crap.
Having said that, I have no idea.