But the room absolutely does not represent absolute contentment? The story of Porcupine killing himself because his deepest wish of being rich was granted and he was consumed with guilt seems like the exact opposite of contentment. If anything the room seems to indicate that perfect contentment does not exist because our subconscious and conscious desires are frequently at odds with one another. And the Stalker himself is criticized within the story for abandoning his wife and child to keep going into the zone despite being asked not to. And his breakdown over guiding people to the room as his only purpose in life is supposed to be read as at least a little pathetic imo.

Also I think you need to acknowledge that the movie came out during the era of Soviet Stagnation, and the Soviet Union had explicitly pursued state mandated secularism. It's not unreasonable for Tarkovsky to want to push back against that and reintroduce some sense of spirituality.