I've had nearly identical experiences-it's amazing what happens when you stop trying to win and start listening. Your approach is exactly right: not pushing back, just genuinely curious about what's working for them. That flips the whole dynamic from seller-versus-buyer into two people having a proper chat about tools and workflow.
What's struck me is that people committed to a competitor often know the problem space better than anyone. They're not sceptical about whether the need exists-they've already bought in, just with someone else. That makes them an absolute goldmine. They can tell you exactly what's missing, what frustrates them, and often they'll mention colleagues or friends who are still searching for a solution.
That "what would you like to be added" question is pure gold. You're basically getting free product feedback and spotting market gaps, even if that specific person never switches.
I've started viewing those "we use [competitor]" replies as research calls, not lost deals. Sometimes they come back when their contract's up or a priority shifts, but even when they don't, the insights are worth more than a closed sale.
Do you reach out to them again down the line, or just let the conversation fade naturally?