Having used Rust professionally for six years now, I share your fear. Like many of the commenters below, coherence just hasn't been a big problem for me. Maybe there are problem spaces where it's particularly painful?

How does the Rust language team weigh the benefits of solving user problems with new language features against the resulting increased complexity? When I learned Rust, I found it to be quite complex, but I also got real value from most of the complexity. But it keeps growing and I'm not always sure people working on the language consider the real cost to new and existing users when the set of "things you have to know to be competent in the language" grows.