When you think about it, Alastor probably kept up with fashion and trends really well up until he died. He's probably one of the more chaotic characters because of that because he can straight up tell you what slang was popular in which particular MONTHS as well as the fashions and the hairstyles. He's basically an encyclopedia about everything from the twenties and early thirties.
But when you think about it some more, he probably would've kept up after his death too, although it didn't matter then.
But after the First Broadcast in Hell, when he toppled Overlords and stole the title, he was pretty isolated. He didn't see much in the way of recent trends, fashions, politics, etc. after that.
So he was basically stuck in this little bubble of his time period because no one would get close enough to catch him up.
I think I would've written him with a form of DID, with his AM radio form (the Alastor we all know and love) and his FM form (a more trendy, fashionable Alastor who speaks without much static and is more commonly seen in a studio environment, jockeying music for his station) because radio is actually pretty fluid.
AM is still something that runs but the quality is different, it has a different vibe, kinda older feeling.
And then FM radio was invented to play stuff and it's what some people prefer, from my limited knowledge on the topic.
But I will stand by my opinion that radio is a fluid mess, because I'm probably not wrong.