I'm not the person you asked this of, but I've worked in museums and research settings and can lob a response your way.
Ultimately, it's that scientists are humans, too. Despite some of them really making their research data-forward, things like tenure, career, funding, and even who would publish your work now and in the future all create normal human environments that reward small, incremental changes to a body of knowledge that don't upset the apple cart, not discoveries that suggest huge changes. In fact, large changes and discoveries can be resisted and denied further research in favor of the status quo.
This is not a new phenomenon by any means:
Both warm-blooded dinosaurs and the Chicxulub impact were both theories dismissed as fringe for decades before overwhelming evidence led to them being accepted as likely. In no small way thanks to Jurassic Park.
Recall that eugenics and phrenology both used to be widely accepted scientific "fact."
100 fairly prominent scientists signed a letter stating emphatically that Einstein's Theory of Relatively was categorically wrong and should be retracted.
Plate tectonics was seen as fanciful crackpot musings for decades. The author of the original theory died 30 years before plate tectonics was even considered possible.
Germ theory was dismissed for most of Louis Pasteur's lifetime, despite being able to literally show people yeast in a microscope.
Helicentrism has a storied past.
Quantum theory was also denied heavily at first. Now it saves photos to our hard drives.
And how many times has the earliest dates of hominids and tool use and human thresholds of development been pushed back by tens of thousands of years?
This is not an exhaustive list, by any means.
So we have ancient examples and modern ones - and everything in between. So the level of education or scientific progress or equipment are not the cause. Humans are. Humans do this all the time. So until overwhelming evidence surfaces, which can take decades or longer, claims like this shouldn't be dismissed out of hand until proven solidly in error. A theory is a theory, so let it be a theory.