How to interpret 主题先行？ This is 张东阁 speaking. I think to understand this, I need to understand the mentality of China in the 1970s, but still, "主题先行" puzzles me. "Themes go first"?? What themes?

我是在上世纪70年代开始剪纸创作。
I started doing paper-cutting last century in the 70s.
当时收到“主题先行”的创作思潮影响，
At that time I was influenced by the "big themes come first" creative tide of thought,
一味追求服务于时代，
I only wanted to serve our country at that time,
抓大题材，
take up the important themes,
抓时代气息，
grasp the Zeitgeist,
因此，
therefore,
在表现手法上大都抛弃了传统剪纸的影响。
in my expressive technique I mostly abandoned the influence of traditional paper-cutting.
主题先行, as you said, it literally means "Themes go first".

But, "70年代" is the Cultural Revolution period, I suppose it refers to the situation that before artistic creation, the central theme has been decided by political factors; people has to do the creation accord with that.


  “主题先行”指十年动乱期间，根据政治需要，先确定所谓的“主题”，然后再根据“主题”的要求填进“人物”和“情节”，使“主题”得以表现的一种文学创作方法。