I think that mostly counts for people from North America (not including Central America), the Pacific Islands, and maaaaybe parts of Africa.
The idea that people in the middle ages primarily wore dark and drab colours is likely rooted in the fact that only clothes of wealthy people did survive, either materially or in portraits, and because historicizing painters in the Victorian era were either copying those late medieval portraits or simply applying their Victorian tastes for dark and drab colours anachronistically to earlier periods, with those potrayals heavily influencing later depictions in other media, such as Lawrence Alma-Tadema and Edmund Blair Leighton, whose pictures are responsible for our idea of red clad Roman legionaries, later gratefully picked up by Hollywood and still too alive even among such renowned reenactment societies as the Ermine Street Guard.
You are not alone, I and many other serious reenactors are here with you.
Do they just look like it, or did they snag them away before collectors got them? I did a quick scan of Google and, while not noticing anything about the literal props being used, it seems a company in India produces masses of stuff for medieval flavored movies and shows.
I don't know for sure, but even if they were simply using props from the same company they certainly didn't request something a bit more authentic to the time period since they have Anglo-Saxons wearing 16th Century helmets identical to what Game of Thrones has many Baratheon soldiers wearing, as well as a strange allergy to mail armor, and some of the brigandines (which are also inappropriate to the period) looked suspiciously Dornish.
It gets even more annoying when those same blatant costuming errors occur in documentaries, when e.g. the very romanised leader of the Batavi revolt Gaius Iulius Civilis (a man who even claimed to be descended from an illegitimate son Gaius Iulius Caesar had fathered during his campeign in the region) is potrayed as a shaggy bearded barbarian, clad in equally shaggy furs.
Actually that is a misconception a lot of people in my country have. That the christian europens were primitive savages Which brings me to the next misconception: europeans were all evil & had nothing better to do than to persecute jews all year round
Just like how 95% of sci-fi/fantasy authors can't be trusted around apostrophes, I've come to the conclusion that 95% of costumers shouldn't be allowed near any sort of animal products. Too often are furs just things to drape over big scary men to show that they are barbarians and therefore primitives, regardless of whether that scrap of fur would stay where it's being worn or even if it would keep the wearer warm which is the whole point.
Speaking of Christians, there's a relatively recent trend of romanticizing European pagans, generally at the cost of demonizing medieval Christians. This is especially apparent with people's attitudes towards vikings, who are very often romanticized and given an air of nobility, and all their raiding and pillaging is summed up as "wow, they were so cool and badass!" No mention of how they drove a massive slave economy that only subsided with Christianization. Stranger still, given their predilection of thinking that "viking" conquests are awesome and not catastrophic, they ignore that the most successful and powerful Norse kings of the period were Christians. Canute the Great and Harald Hardrada (why is his name never translated as Hardrede, it is the appropriate English translation) would laugh at Vikings' Ragnar Lodbrok if they somehow met and Ragnar presumed to boast, and probably also mock his shitty clothes as well as his faith.
