Here's what we have:
1) In-vitro and animal model data showing metabolic and reproductive harm from plastic contamination
2) Plastics continuing to be found contaminating more and more things that humans interact with or ingest
3) Strong evidence that this contamination bioaccumulates within individuals
4) Strong evidence that this contamination accumulates across generations
5) Strong evidence that this contamination is approximately impossible to remove from water and soil
6) Strong evidence of very similar metabolic and reproductive harms that have been found in-vitro and in animal models showing up across extremely broad swaths of the human species.
I would buy into the, "no alarm until we know it's dangerous" approach if there were a way to undo the harm after the fact, or if there were a way to quickly "know it's dangerous," or if this contamination wasn't covering pretty much the entire globe, but none of those things is true.
We have no method to ascertain population-scale danger prior to that danger being pretty much irreversibly realized.
I've identified what would change my position from alarmed to not-alarmed. What, concretely, would change your position from not-alarmed to alarmed? There is no way to do a randomized controlled trial of plastic poisoning. So what would constitute "knowing" it's bad for us?