> past an age a fellow just wants to learn a single reliable stack and collect a weekly paycheck

That's a bit too strong. Surely there are people like that. But I'm "past an age" and there's always some newish thing I'm learning. However, I'm in no rush to start adopting them for real projects. I want to know the payback from switching, and neither hype nor the word "modern" cut it. I want to know what this language is good for and what it's not so good for. So I learn things and evaluate them, and over time I add things to my working set of languages and tools.