What's critical about Lister Pro?
The ability to easily save a customized lister, perform bulk actions on results, and have convenient, end-user access to tabular views of large content types that are too cumbersome to manage from within the tree control. This is standard functionality in any CMS worth using, and essential for the vast majority of sites I've built over the last 20 years or so.
It's a bit silly, IMO, that you can't do these things with the built-in lister. It feels intentionally crippled solely for the sake of selling the commercial component, a perception we want to avoid. I wouldn't build anything more than the most basic, trivial processwire-powered site without Lister Pro, whereas I could easily do without the other pro modules. I (sometimes) use Form Builder out of convenience, but Lister Pro out of necessity.
Mind you, I'm not complaining about the cost, at all. It's entirely reasonable and I'm happy to support development. But if we're talking about the road map for the core, open source project, I most definitely view Lister Pro as essential functionality that absolutely should be part of it.
I am intrigued by the idea of "graduating" pro modules to core modules via some process that combines hitting some financial goal with enough general community interest in having specific functionality available in the core.
Just my two cents.