I'm going to start off by saying I would recommend watching The Gorge as blind as you can. The trailer doesn't spoil much but it does reveal the framework and direction of the story. If you like the 'vibe' or setting of Annihilation though you may like it.
If you don't mind a bit of a reveal this is what I mean by the last part:
spoiler
Both movies are about a quarantined area where mysteries lurk.
It's near-future sc-fi but leans a bit more into horror and action than Annihilation.
Here's what I liked and disliked about the movie (real spoilers):
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I went into The Gorge after only seeing the movie poster so I thought it was going to be some kind of Cold War-style forbidden love movie. I was glad to see it evolve into something else.
What I liked the most was the setting and premise. A heavily defended remote and isolated area full of mutated mysterious creatures and plants where attacks are infrequent but when they happen they're in World War Z style is something I find neat. I feel like I see elements of this regularly in video games but less so in movies.
Once they were inside the gorge I would have liked to have seen the mutations as a bit more grand or awe inspiring like they appeared in Annihilation. Maybe a bit less humanoid. That might be a bit hard though considering how dark and foggy it was and how they immediately were trying to get out rather than explore.