That's the discipline of data-driven business. If 20 people use your app and despise it and are depressed by it, that's better than 19 people using it and loving it. No sentimentality allowed.
Usage can't be it, because I use a ton of software that I despise and get depressed by, but only because I get paid to do so, or the app is so niche there isn't a viable replacement.
You'd have to actually talk to your users. But that requires genuine human investment, so it doesn't scale. It doesn't come in the form of a third-party SaaS with a pretty dashboard, generous free plan, and integration via single <script> tag.
In short: they could measure this, they just don't bother to.