How do you compare it to the Portal games or the Talos principle? I find those superior in puzzle mechanics, sense of achievement and playing dynamics. They can be challenging but you never feel aimlessly going around without a purpose like the Witness. There is good review of the game on youtube by the title "The Witness - A Great Game That You Shouldn't Play", it covers a lot and resonates well with my experience, the panels could've been a standalone mobile/tablet game. Everything else in the game is beautiful but frustrating.

https://www.youtube.com/watch?v=KZokQov_aH0