The song sung by old engineers who refuse to learn new technology, so they try to make knowing few a positive (it isn't). The classic "It's not a bug, it's a feature!"
I don't think the core of a good developer has changed much since the early 90s. You still want people whose skill-set is T-shaped... You want them to go deep on at least a few domains, but you want them to have broad experience in lots of them. The broad experience makes for developers who are better than the sum of their parts, can adopt solutions from other domains and can communicate better.
I generally won't consider too seriously a "senior" engineer who has only a single "class" of knowledge. I realize that sometimes they have limited control over this (the jobs they happen to get, yada), but I just want the best developers... and in my experience they find a way to follow Norvig's advice and at least toy with some of the major flavors: DBC, functional, class, syntax, declarative, concurrent, parallel...