You know what? This is a really great point. When I reflect back on my career experience (at companies like Expedia, eBay, Zillow, etc.) the best distributed systems experience I had was at companies that standardized on languages and frameworks and drew a pretty strong boundary around those choices.

It wasn't that you technically couldn't choose another stack for a project, but to do so you had to justify the cost/benefit with hard data, and the data almost never bore out more benefit than cost.