Just because it is not complicated, does not mean it is not hard.
Common sense means that such knowledge is held in common. Are you suggesting that most people understand economics?
1. If lots of people want something, the price goes up relative to what it would be if fewer people wanted said product (and vice-versa)
2. If lots of people have and/or produce something, the price goes down relative to what it would be if fewer people supplied said product (and vice-versa).
3. Incentives matter.
Most everything follows from there (if applied rigorously), and point 3 is the most important point in most cases.
Those three ideas are useful, but I would not say that they equate to an understanding of economics. What about the subjectivity of value? The value scale? Why people save? The effects of capital accumulation and distribution? Time preference? Etc. etc.