I disagree. RoR is great when there's moderate complexity. Microframeworks (Sinatra) are better for low complexity, and everything with high complexity is a unique and special snowflake.
> Magic is wonderful when it works right, and painful when it goes wrong
...and really educational when you start digging into it, and then you generally realize it only went wrong because you were trying to do something stupid.
> the remaining 20% takes up the remaining 80% of the time
Sure, but that's because the first 80% took a fraction of the time, not because that last 20% takes a multiple.
Do you have a particular example?
> spooky action, highly declarative style that RoR encourages
This is a bit of a "cognitive style" difference. In most of RoR - particularly your models - you want to be describing the idea of the thing. Since most people start programming by writing procedures, this is a bit of a leap. RoR Models are not about how a thing gets done, but about what that thing is. When you think from this perspective, RoR models are easy and nice.
> Beyond that, with the failure to understand the before and beneath...
Straight up, I want you to explain the complete before and beneath of your favorite tech stack or this is problematically hypocritical. I would then also want you to explain why it's reasonable to expect this of all programmers, rather than just senior programmers.