The Indicator of the Closeness to Reality

Wenn ich nicht ich wäre
wäre ich nicht hier.

If a teacher were a student, he / she would also day-dream in class.

Good. This shows I understand the subjunctive. But subjunctive as an indicator of the closeness to reality? No. It merely is a way to express wishes while showing the world that you know it is only a wish.
It is also used hypothetically. I can imagine, too, a mechanics question with lots of wäre and würde.

I can imagine, too, a diary entry.