All of the characters are constantly arguing with each other. The story line requires constant suspension of belief based on the endless succession of improbable events and improbable character behaviors. Contradictions with earlier episodes and even details within the same episode. It's really bad. I hope the final episode redeems it but I have my doubts. I want to have an LLM rewrite season 5 and see how much it improves.
Idk, the grey goo for instance. It melts steel and concrete but not people and killed soldiers but not main characters.
There are also stupid leaps of faith like Holly's mom hobbling out of bed and sticking an oxygen tank in a clothes dryer(as if that would even do anything)...