> But without trying for millions of times, scientists won’t find the one drug that works.

well isn't it mostly other way around? millions of times to LOOK FOR hidden SIDE-EFFECTS?

animal testing is mostly for answering 'is it safe?'

Sacrificial animals are used to answer nearly all questions in medicine. I would be surprised if you could find a single therapeutic out of the last 3,000 that entered Phase I that didn't cite mouse experiments in its preclinical studies for efficacy.