You've done a really nice job summarising a very complex topic, many threads to pick up on, but I'll go with the personal experience of academia....

Basically I had to quit my PhD because of lack of money and pick up teaching A-level sociology... which means I was forced into becoming more of a 'generalist' - after 16 years teaching it, I now have a very broad knowledge of a whole load of sociological issues, but without having the very specialist knowledge in any of them.

However, when I look over at my Doctored colleagues who have stayed very focused on their specialisms, I don't really see that much happiness exuding from them! Which is odd, given that they are experts in their fields.

I think within academia at least the rigours of the discipline make specialising a real chore, until people get to the top of their game (I'm thinking Giddens and Bauman in my discipline) at which point they seem to just be thinking across disciplines... bringing together philosophy, politics etc... so more of your polymath. Although to get there probably does require a deep-dive into one specialist area.

From my perspective as a generalist I've also had more scope to play around with different forms of presenting knowledge (data vizes) and so on, so it's been quite fun.

Having said that I do have one specialism - exam training, and it's nice to at least have that because it's quite lucrative!

Just the psuedo academic's perspective on the matter... trying to specialise on how it applies to one general area (tricky words those two... specialism and generalism....!)