Usually, what I hear from folks is that you come out of using Mithril with more transferable knowledge than something like React.
One example that comes to mind was when someone realized you could implement an incredibly simple atomic CSS composition framework by basically doing this:
/* some atomic CSS */
/* a bog standard CSS selector string */
const MyWidget = '.primary-color-700.pad-700';
/* a Mithril element */
m(MyWidget) // <MyWidget /> in JSX
Now compare with what one would do with most frameworks: one would pick some CSS-in-JS library, get things done and over with, but probably learn nothing interesting in the process and have little idea of what sort of code is actually getting shipped to customers.