I am going to start by saying this was the movie I was most looking forward to, and NEVER expected to exist. That being said, going forward will have spoilers.
We start off with a strong beginning to the movie. There is anticipation, tense scenes, and the gore you expect with a 28 movie. The island they then show you, is creative. The high and low tide access path adds a risk when leaving but a comfort when staying. It adds a time pressure that is constant throughout the start.
Things begin to go downhill for me when we are introduced the "Alpha" infected. This infected is bulky, strong, muscular, and leading the pack. He also only ever rips heads off of people like the predator and leaves the body behind. I do not recall seeing him eating anything, so maintaining his body while the others who eat the scraps are scrawny leaves me a tad confused. We also got family drama among survivors and.... infected? Not only is the Alpha the main killer, but he is also a father! His baby momma births a non infected baby the survivors take, and he goes crazy when he sees her dead; focused on chasing them down. If I could change anything, it would be this whole Alpha situation. Think of an ant colony. Perhaps we have scouts that seek food sources and notify the pack to attack in a herd? In the previous movies we see the infected eventually starve and die, which I think plays into the memento mori mantra a bit better then whatever is going on here. It seems the "rage virus" was previously introduced as this killing, destructive, violent disease. Not necessarily re-creating life but consuming. Yet we got infected having babies now.
I do like the human nature this brings however. In the first 2 you can see recognition sometimes among the infected, reinforcing that these are infected people. Yet, with the whole Alpha thing making babies - this raises questions for me from when Don killed his wife instead of mating with her.... we have more open plot points that aren't fulfilled and conflict with the previous lore. Among all this we have a son trying to get treatment for cancer doomed mom, a dad who is cheating, a crashed ship of military who show up for a few scenes, a doctor who is building bone towers, and 2 different "types" of infected now.
As per the complaints of nudity among infected, think about it. They are animalistic. Clothes will tear, rip, and be removed as they run throughout the forest and they aren't really stockpiling a closet or caring about cleanliness. It makes sense that they are "hanging dong" as these complaints would say.
There is 1 more plot point I found disappointing which shows at the end. After a beautifully filmed scene where Spike is roasting a fish and infected show up, reflecting that gritty film style from 28 days, we get whiplashed by this 80s rockstar wannabe bleach blonde, pristine clean jump suit 6 person pack of "jimmy"s kick flipping to metal music to save the boy from a group of infected. Thats the end. I cringed so hard I wanted that fight scene to end so bad. I'm nervous about part 2.
I am worried they are going more toward a failing comedy with shock value, rather than a horror/thriller.
I recommend giving the movie a shot and forming your own opinion. If you have no former investment in the 28 series and are new, you'll probably like it, as this did not serve much for existing fans.