Yeah, the fact that they're at odds is what makes this a difficult situation. Right now I'm leaning towards: this other domain is close enough to my old domain

Yeah, the fact that they're at odds is what makes this a difficult situation. Right now I'm leaning towards: this other domain is close enough to my old domain that given work's context in my overall life, the pay makes it worthwhile to compromise on my work goals, as long as I'm able to "leave the door open" to re-enter my old domain. That probably won't happen at this company until the other, more experienced engineer who took over my old domain leaves, and maybe not even then. But the magnitude of the pay difference is great enough that a couple, few years of the dot product between what I'm doing and what I'd like to be doing in my career is ~0.8 rather than 1.0 is worth it in my life right now, given that I want to eventually buy a home in my high COL city. I think having been in the situation where I felt I was basically in my dream-job and knew I was, makes it harder to have lost it, even though I am in a really good spot in my career overall.