(mindset = established set of attitudes or way of thinking)
It seems to me that too many students (and teachers!) have a "grammar mindset". They believe that complex structures are the key to a high IELTS score, and they focus on learning rules. As a teacher, I notice that these students are quick to question me if I say anything that seems to break a rule; they assume that I have made a mistake.
I prefer the "vocabulary mindset". Students who have this mindset are more concerned about how native speakers really use the language. They collect words, phrases and collocations by doing lots of reading and listening, and they enjoy using the new vocabulary that they have copied from these sources. As a teacher, I notice that these students are quick to question me about any new or interesting phrases that I use; they want to learn how to use those phrases themselves.
To me, the vocabulary mindset seems much more positive and proactive than the grammar mindset. It seems less critical and more curious, and I also think that it makes language learning more fun!