I think that gap exists across most all languages and libraries with the possible exception of things that are in such heavy commercial use that most of the people interested are doing it specifically for a job. There is just too much out there to learn and only 24 hours in each day. I know that my stack of unread technical books seems to grow each year. For languages, I would like to pick up Rust, but I’m slightly more interested in Idris. At least with Idris, I’ve gotten a few pages into the book.