Capitalism teaches you specialisation is the way to go, and survivors bias is how is shows it to you. Meanwhile literally anyone at the top of every pyramid is some version of a Jack of all trades.

I'm an equally bad programmer and bad designer 😅

I'm one and a half. A designer that knows html/css and code logic but not code language. To be honest, its just difficult, considering that you also need to know business and marketing too, and and and to make things properly take off. I know those too because I took a decision early on (for myself): Learn everything or learn coding. I chose everything.

Speaking as a leader of software teams, some cross training is nice in order to spread knowledge and insight but I’d prefer to have team members be subject matter experts in their disciplines.

I'm not sure if people will get the reference 😅

its a great control mechanism, to not allow someone to become a subject matter expert in more than one discipline. Hence the modern "goal" to be in a vertical big corporate.

I would never disallow or punish or force.