It is what it is. If you just read the easy stuff, you will just be entertained by it but you will never grow from it.
What that line really means is that you if you never actually read complicated stuff and try to understand it, you will never learn anything at all. One of the biggest examples is that of the Bible. The Bible is so complicated and hard to understand but once you understand it, you have enough knowledge to survive in life without getting into trouble. The same applies for everything.
I can further go to say that Social Media networks are killing us in that sense. They are making us forget on how to be complicated. What I am trying to say is that sometimes complicated stuff are better than the simple ones. If you don't get it, it is because you are not used to complicated stuff.