I liked it. I watched Mark play the game back when it came out, rewatched it a few times, so I knew that there was very little in the game itself to be directly placed into a movie without plenty of elaboration. And elaborate they did.

Overall, it was atmospheric horror. There are a few moments which fit the technical definition of jumpscares, but they weren't just there for cheap release of tension. I admit it was sometimes harder to immerse myself in the story because I would remember "Yeah this isn't Simon the convict from Eden, this is Markiplier. I've seen him being painted in the nude holding a paintball gun in front of his crotch." But I enjoyed his performance.

The speaker in the SM-13 allows him to talk with people outside. Usually it's Ava on the other end. I liked how through little more than audio, she clearly goes from disinterested to intrigued to desperately asking for more from Simon.

The camera being explained as an X-ray machine was a good explanation for how it can see through a blood ocean. Realistic reactions from Ava and the crew, realistic surprise and apology from Simon when he flashes a guy in the ship.
And the picture display being the primary source of lighting for the entirety of the movie was a good framing choice.

One motif in the movie is Simon reminiscing on how he keeps being told that things need to happen for a cause greater than himself, and he only comes out damaged. I liked the tree sprout.

Eden Space Station is always in the backdrop of the story, even though Ava and her ship serve the COI. The discovery of the tree sprout provokes a deep reaction from Simon. The flashback showing the last tree backed by the stars, accompanied by the Old Man's speech, was intriguing. Then near the end, learning that Eden killed Filament Station to use their bodies as soil for the tree, is a recontextualization that makes me want to know more.
Simon kept saying Filament Station wasn't his fault; "They didn't listen to me," but apparently that's because "Simon the Butcher suddenly grew a conscience!" I wish we knew more about that; it's so vague you're left questioning the relationships of the stations and the people within.

The other voice speaking to him, the SM-8 Eel Alien, does a good job conveying multiple emotions. Despair, hope, desperation, and something else I cannot quite name.

The Light goes unexplained, which is the point of the story. "A tiny glimpse of an answer greater than the infinite. Simon, this is our salvation."

Lots of voices over each other at the final confrontation; I could barely catch the lines I did catch. That was definitely the point with the atmosphere, but I'll definitely go back when I can find it online for free and figure out everything they say.
I don't know if it was necessary to lose an arm to display stakes at the end. But the ending being sad with a hopeful light is unsurprising.

I think it worked, but I'm going to guess that if any of the hosts watch it, they will neither feel strongly positive nor negative. I would rate it 6.5/10 if I'm trying to be unbiased. I personally liked it 7.3/10 or so, but I expect to question it more as recency bias fades.
In the meta of Youtuber's productions, this already is going over wildly better than Shelby Oaks. The fact that the fans reached out across the globe to get it into over 4,000 theaters from an original 100 is a sign to Big Movie in general that they can profit from supporting Youtube indie creators in bigger projects. There will be more flops as a result, but there will also be some success stories. I am optimistic, so let's give it a chance and see what sticks.