I think there are different reasons for the various issues you are raising here. I think partly the issue with the pyramid is that people like ancient mysteries, and it's fun to think that they were built in some unknown way. Many people also grew up being taught that it was not certain how they were built, which is then hyperbolized to "we have no idea how they built them". Furthermore, people cannot all keep up with more recent thinking about these things, so those ideas get stuck, and then develop into sort of a persistent urban legend.

Vaccine reactions and climate change I think have other issues behind them. Some may overlap. Tribalism may be an issue with climate change. Due to clever marketing, it is an issue that has now been packaged in the general conservative platform, which makes it easy for low-information voters to decide their stance on the issue. Pair that with readily available sources constantly questioning the validity of climate change and people selecting information which reinforces their already held opinions, and it gets difficult to correct that viewpoint. Anti-vaxxers are another issue as well. Modern medicine and society has allowed us to be so healthy that people can no longer tell the reason they are healthy is mostly from vaccinations of the population, sanitation, water quality, etc. Its easy for them to attribute health to "living naturally" and they have a suspicion of corporations. The one (later retracted) study drawing a link between vaccines and autism was the only seed needed for the persistent viewpoint to hold, and efforts to discredit it are viewed as the corporate line.

Regardless, its one of the costs of living in a society which does not value education, and actively tries to distill complex information down to talking points, as well as having a binary political system.