1. The volunteer plot hole.
If people wanted to be tested on, they'd just volunteer. There are plenty of folks who are terminal, only have months to years to live, you could simply pay them to volunteer to go to the cover to see if the treatments work rather than subjecting unwilling participants to crime. Pay their families enough and they would be more willing and you would not have to be on the wrong side of the law. Why do you think doctors do "experimental" surgeries all the time? Because patients have no other option anyway. If said patients were on the island for 2 hours (4 years?) and lived, you could helicopter them out. Basically it would be a "Let's get this over with" mentality for patients. A lot of people would be interested in that.
2. Really gr*ss weak-bone lady scene.
I mean yuck dude. Just gr*ss. Why did you have to do that? No one needed to see a lady break her bones and then heal rapidly, like we get it, that's possible within the context, but that's just gr*ss. Additionally, her illness was a calcium deficiency, so what's with the combined mental illness that makes her want to break her own bones? She literally tried to m**der the other two characters, why? What was the context even there? Because she didn't like them looking at her due to her back being hunched? That makes no sense.
3. What you did to the youngest folks in the film.
Did you really just have two people who were 6 years old that same morning have a baby of their own? Really? That's pretty much as cringe as it gets dude, why even include that in a film? Did you just have a stroke while writing the script or som*thing?
4. The repeat awful line delivery
Ken Leung (Jarin) delivered his lines basically as humanly horrible as possible. Is that guy even really an actor? Watch that dude's lines exclusively and you'll think he was doing an impression of Mark Zuckerberg. Other actors struggled at points as well, but holy crap did Ken just own the title of worst actor on set... and actor was a literal baby.
5. Having foreigners act in your movie doesn't make it good
Vicky Krieps (Prisca Cappa) made the film feel very indie and low budget. I get that she has an accent and that is supposed to make it all feel more diverse and interesting but she got second place for worst actor on set. There was pretty much NO emotion in the majority of the lines she gave and it felt like she was just picked for the role because they rant out of money while casting.
6. The irritating portrayal of old people
Toward the end, the original mom and dad get super old, and they're just smiling around each other, they look about 65 but they're acting like they're 97 year sold. They're smiling a lot (when there is literally nothing to smile about) and acting like everything is la-di-da when that's not at all how most any old person would act in that situation. Then they suddenly d*e, despite again, looking like they're only 65. That's right, both of them d*e, one right after the other, I guess the average life span is actually 65 guys, so, that's som*thing to look forward to.
7. The "greater good" scientists.
The scientists brought in tons of people who were not even sick, and made them basically pass away with the people they were studying, why? If you're going to claim the moral high ground, what is with dragging all the innocent people with those who aren't even part of the study? Major plot hole.
8. The "black out" concept
Why is it when people entered the beach, they would feel nothing, everyone was calm and normal, no idea they were aging a year every 30 minutes, but when they try to leave (which would likely feel much much better as their aging would slow down) do they black out? Hello? Wouldn't you black out from time suddenly speeding up x a million vs it slowing down?
9. Aging does not affect dead cells, but it does dead bodies?
Wait, if hair is essentially dead, coming out of your body... which is why no one's hair grew super fast... why did the dead bodies rapidly decompose? Aren't your cells mostly dead when you d*e? I'm so confused!
10. The most obvious escape plan, ignored.
No one ever tried the escape plan where you just take steps slowly out of the cave to escape... why? Why didn't they all just slowly walk through the cave at the same time? And what made them literally turn around and walk to the beach while "Blacked out" wouldn't they just pass out in the cave? But that would be a problem right? Because no one would recover them? So you inexplicably just had them walk themselves back out of the cave then pass out... nice.