The story is almost a cliché of many preceded movies. The paradigm of getting rid of a group one by one has been used excessively. Blood scenes were made with good taste without having violence that we used to see as a stereotype of this category.
Disconnecting the internet and phones were an exaggerating idea since patients had access to the whole facility. Also the feasibility of leaving the facility but insisting on staying at it were unbelievable.
Last, but not least, the medical background of volunteers is questionable. It requires lots of knowledge even for physicians to be aware of all that.
The ending was good, but the whole experience was below satisfaction.