I googled the question, "How many people finish a videogame" and got the following: "According to some industry experts, only 10–20% of players finish a new video game. A 2019 study of Steam achievements found that only 14% of players completed the games they owned."
So I don't think these Hellblade stats are that unusual. I'm not defending the game - haven't played it - but a 10% completion rate vs. a 14% average completion rate isn't a huge difference.
It's interesting how few people actually complete their games. That's a different topic, though...