> Moreover, a lot of the libraries in rust needs you to understand the type system thoroughly sometimes to use them, and some of them use the typesystem to enforce some specific behavior (without telling you :-)). For example, the logger mechanism in rust makes it very hard to dynamically change the logger implementation at run time but it doesn't explain why (in the end, I think it has to do with thread safety, but I'm not sure).

Mainly because logger is a static value, if you really want to change your logger at runtime, then you have to pay a little bit for synchronization (i.e. locking with mutex), other than that, it's not that hard.