It didn't feel slow to me. I will say parts are atmospheric, so if you find being immersed in an alien land to be off putting you may find those scenes not to your liking. There are scenes where the acting is more subdued, but that channels the realism and sense of unease to me. When there are action scene I'd say they are pretty intense, one in the middle in particular is terrifying in way most horror films fail to achieve.
I don’t find being immersed in an alien world off putting. I do find unnecessarily slow movies off putting though. The movie is on Netflix anyway so no huge loss if I watch it.
Hard to determine that as much of it comes down to what you find interesting. I can find a scene enthralling that others find boring.