I welcome the challenge to be forced into learning new things that are outside of my expertise.
I'm a backend dev and a few years ago the company pivoted and put almost all the engineering team on building a new React app. I'd never done React. It took me some time to learn it, and I'm still bad at making things look pretty. The skill will be valuable when I look for another job. Now I can apply for Full Stack positions and not just the backend positions.