Again, you just used the present size of a nation's economy to argue that a nation isn't in decline when someone was talking about the ongoing decline of a nations politics, economy, and culture. It seems odd to me you're able to, for other countries, understand that the present moment can be viewed with both historical and likely future context.

>The "prominent UK residents" don't "leave" the UK. Benedict Cumberbatch lives...

Plenty move, but that wasn't the point I think anyone was making. If I wanted to say they were moving to the US, I would have said that instead of "leave to participate in US industry". And all of that ignores that the original commenter was talking about the decline of British media rather than saying that they're aren't talented Brits. It's not like they they're saying the UK had a bunch of great actors ten years ago and they suddenly died. Them working in American industry rather than the UK producing it own is, I'm pretty sure, the sort of point the commenter you replied to was making.