In all the companies I have worked at and have looked at such docs, unfortunately this doesn't really work because those internal documentation sites are statistically never up to date or even close. They are hilariously unclearly written or out of date.

As for relying on the code base, that is good for code, although not for onboarding/deployment/operations/monitoring/troubleshooting that have manual steps.

^this, but many non-code documents with manual steps can also be kept up-to-date as long as there is a way (a) relate it back to the codebase or another source of truth (b) detect conflicts (when someone says something in contradiction to an existing document)

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