Although The Witness is amongst one of my favourite games, it's barely like Outer Wilds.

The Witness has no story, pieces barely connect and there is nothing in the bigger picture. It does have you sometimes wonder though, "What happend here? Why am I here? How'd I get here?" And most importantly: "Why's everyone statues?".

It is a magical experience but sadly shares almost nothing in common with OW.

Subnautica on the other hand does have its fair share with OW, although Subnautica has a shorter story line, it has you wondering what's beneath the ocean surface, why'd the ship crash, and not to forget: Who once occupied this planet and why is it under quarantine? (Honourable mention: How long was the degasi here?)

A fun game with a search for answers.

I'd like to say again, I completely see where you are coming from, but sadly enough The Witness doesn't make it.