It's not one particular thing that broke Metroid Dread's spell for me. The real issue is how fundamentally unfriendly it is as an overall experience. It's challenging, but that challenge is a solid, vertical wall here. There's nothing in the way of help for players who can't climb that wall. You're expected to just be patient, keep trying, and, to borrow one of the more annoying gamer troll catchphrases, "get good."
I don't want to get the kind of good that's required here. I tried and it was deeply unpleasant. When I got stuck on a certain boss for multiple hours, so much frustration built up in my repeated attempts to beat it that there was no satisfaction when I finally succeeded. That was a recurring issue with boss fights, with pathfinding, and even with some of the later run-of-the-mill foes that you encounter. The more I played Metroid Dread, the less I wanted to keep playing. I didn't manage to finish in the end, and I'm sure I never will.
It's a damn shame. I love Metroid. I want to play all the Metroid and experience its whole story for myself. But MercurySteam decided, for whatever reason, that only those people who pass the test, who master the controls, who happily throw themselves at challenges again and again — who, to use that atrocious shorthand again, get good enough — can experience all the joys and wonders that Metroid Dread has to offer. What a waste.