Sounds like the bad reviews are people who feel their Asian race was not represented in the movie, people who think just because a movie is set in a certain country in this case Singapore means everyone from that country is swimming in wealth, materialistic and shallow. Then Americans must love blowing up planes, buildings, cities based on the Die Hard movies I used to watch. Also Westerners who just can't stomach the fact that hey Asian people too can have it all and yes they don't all live in mud huts and speak bad English. If you just watch the movie and forget about the skin colour of the actors, who cares what country it was filmed in and accept it is all fantasy and Hollywood entertainment. Nobody is asking you to be crazy, materialistic and rich just like Die Hard is not asking you to take on terrorist groups and jump off burning planes. It's a romantic comedy with a poke at Chinese culture and the generation gap. People just read too much into it and you know it made an impact as haters bothered to hate.
Review of Crazy Rich Asians
