> "Doctors slow to..." Implies all doctors.

This kind of generalization is normally read as "Typically, doctors [as a profession] are slow to…" rather than "Literally every doctor is slow to…". TFA supports that statement with a metric and some reasons why.

> What's more likely: that the hardest working, highest average IQ professionals are slow to adopt something that would help them save their patient's lives? Or that the writer of the article is biased and exaggerating things?

The former. Most doctors work within systems, and can't just start using new tools they think look neat. Instead, they use approved (often mandated) tools.