reddit user SteveA000 recommended @steveklabnik comment from reddit:
https://www.reddit.com/r/rust/comments/1fofg43/comment/lopwnyd/
Just to provide another perspective: if you can write the programs you want to write, then all is good. You don't have to use every single tool in the standard library.
I co-authored the Rust book. I have twelve years experience writing Rust code, and just over thirty years of experience writing software. I have written a macro_rules macro exactly one time, and that was 95% taking someone else's macro and modifying it. I have written one proc macro. I have used Box::leak once. I have never used Arc::downgrade. I've used Cow a handful of times.
Don't stress yourself out. You're doing fine.