“The learning itself is constructive (huge understatement) even if it does not lead to kiruv, rabbanus, teaching, etc. It’s called Torah Lishma.”
The learning is only constructive if it has a positive affect and refines the one who learns it. Many leaders of the haskalah were learned men.(No, I’m not C’V equating the 2 – I’m using an extreme example to make a point).