(Do We Have This One in some form? It's not actually a trope, obviously, but I'd think it deserves a page as it's a useful concept, and one well-recognized enough to have a page on The Other Wiki.)

"I don't care what happens to these people."

A phrase coined by Dorothy J. Heidt in a science fiction-based Usenet group in 1991 to describe an Audience Reaction to a work of fiction where the characters are so universally bland, unengaging or unlikeable that the reader simply loses interest in their fate and, by extension, the work as a whole. This can happen with or without the presence of more objective shortcomings, but the most interesting examples tend to be those where this is a critic's main complaint, single-handedly dragging a work down from near-perfection to almost completely unenjoyable.

Extremely subjective, of course, so don't add this as an example on a work's page unless the phenomenon is referenced in-universe.

Also often stated with added emphasis as "I don't care what happens to these people".