Studying English grammar should be approached as trustful confirmation to what learners are discovering from actually using English everyday.
To me, the biggest mistake of many teachers in S. Korea is treating English grammar as REGULATIONS to be instructed BEFORE using English.
Without actually using English, learning CONVENTIONS or USAGES from other examples FIRST, just knowing REGULATIONS will not help you at all.
Let’s admit. We are spending TOO MUCH MONEY for English education, and yet there are still TOO MANY PEOPLE not doing well. It’s wrong.