Build times have regressed considerably the past few releases (at least for me). Not that I'm complaining about the tradeoffs, the new features are generally worth it. Whats most annoying is that it's often hard to tell which features are expensive until you've already wasted a bunch of time introducing em.
But I've got to say I'm super jealous of the level of introspection the rust compiler allows here. I'd definitely be willing to change a few C# coding patterns in code bases I maintain to benefit build times, but as is, that's a really painful trial and error process. And sometimes you get lucky finding the root cause, but if you don't... well, it's not a great experience.
In my experience C# compiles faster, but I still agree with you on all points.