> curmudgeonly old guys say, "I know better" and quite a few of them do
Oh, absolutely, we often do. But, like the ancient kungfu master trope, you can't tell your juniors this directly, it's a realisation they have to reach themselves. Sometimes while being smacked in the face by the consequences of not listening.
(More seriously, being a curmudgeon doesn't help; being a mentor does)
The other day, a promising young programmer asked me how to deal with the overwhelming load of new frameworks. Which ones should he learn? Which ones should he ignore? What should he do if he picks the wrong one? How will he know?
In my opinion, it really doesn't matter as long as he is learning something new. You only get stuck when you try to stick to the things you are familiar with. You need to keep stretching yourself time after time.
If someone says to me, "Do it in Python", "Do it in Elixir", "Do it in Haskell", "Do it in Go"... it just doesn't matter to me. I've been through that blender before a hundred times. In fact, that's precisely why you would pick a guy like me. I'm not trying to keep up with the current trends. That doesn't matter. But I'm also trying not to hang on with a death grip to what little I know.
On the other hand, if you need some guy who knows every single detail of how Rails works, hire a young guy who has only ever worked with Rails before. You need a mix on a team. Pair him up with an old guy so that he gets some perspective before he burns out his career.