It's not like it's ever been unusual for novel adaptations to be like this. An anime gets one season, sometimes whether it went spectacular or not, "go buy the novels for more." A manga ends abruptly after teasing much bigger future developments, "novels carry on from here~." I'm just saying, there's a difference between something getting shitcanned against their will and something that was always intended to be a teaser to boost sales in the original medium. In the grand scheme of the entire story, yeah this is a "rushed ending," but it's also a pretty obvious cliffhanger that's begging you to go suck off the novel publisher.