Popularity and marketing is a factor to the extent that lesser known movies will not get enough reviews to count. Note that some movies gets ranked lower despite having a higher percentage. E.g Citizen Kane has 100% but is ranked several steps below Black Panther which has 97%. This is due to Panther having more reviews so the confidence is higher.
Well, we tend to review what's new, not something from decades ago. Different process. It's unsurprising that there are more software-countable reviews of contemporary movies.
Black Panther, to use the example some are protesting here, is a perfect storm of recent (max accessible reviews), critically acclaimed, and wildly successful commercially.
I think it's more telling that recent Star Wars movies like The Last Jedi are on the list, but A New Hope and The Empire Strikes Back (which are more important imho) are not.
This is one reason I like the standard set by the Cocaine and Rhinestones country music podcast. He won't talk about 21st century music because we don't have enough distance to tell what's truly great from what's merely popular at this point. A couple of decades of reflection really separates the great from the trendy.
