Is it me of everthing I've seen from this place looks like from the 1950s ?
Trends change due to popular demand. There is no popular demand in North Korea, so nothing advances. Their whole culture is based around the idea that they have a divine origin and the Kim family is ordained to lead them. If everything was "perfect" with the first Kim, Kim Il Sung, in the 1960s, then changing or updating anything would be saying that his style was not perfect. It's an endless loop of "Kim showed us the perfect life in 1960, so we all live in 1960 forever and anyone who wants anything different is a heretic."
Source: Trust me bro