Most obvious flaw is that it is scientific theory, so you have to read a lot. Most people aren’t willing and/or able to do so. Details are also not intuitive (as Marx states himself in book 3 of the Capital), so it overall makes it hard to spread and maintain in a sea of vulgar economic practice that just “works”, not to mention every media average Joe living in DotB is consuming is owned by the bourgeoisie and 100% antimarxist.