As a native English speaker, keen feels like a very 1950s TV word. Don't know if that's actually true but feels like that way. I expect you're more likely to hear like cool today are some more contemporary word.
Saying "I'm keen to do x" or "he's keen to do y" is a fairly common normal usage but having said that, wouldn't normally be my first choice of language as a millennial, maybe does sound a bit old fashioned
Oughtn't really affect emotive language like 'keen', though.