an untapped genre
You did that on purpose, didn't ya ;-)
they need a LOT of content to really keep any type of long-term interest
I am not sure what you mean with content.
I did play things like Cookie Clicker and Clicker Heroes. And those games do not have content in the way Queen's Brothel has content.
Clickers live from their optimisation mechanics. Eye candy does of course not hurt and some alibi fluff. But game mechanics are core. Queens's Brothel on the other hand is basically a kinetic visual novel with some illusion of choice. But it is just telling a linear story. No player input needed. Besides literally clicking. In that regard, clicker games are less clickery than many other games. They do have more grinding though. Lots of it.