and... the 'impostor' thing... quite true. easier for these people to slip in to larger companies, I think, but it's a problem all around.
I would expect someone with 20+ years of experience to be able to help juniors troubleshoot in any language/stack, though, whether they expect it or not. :)
I can with one, and have cracked his management style too, so he's gone from being unproductive and the butt of office gossip to meeting schedules.
The other is new to this country, doesn't speak much English (e.g. not enough to ask questions) and understands little English too. At a loss for how to proceed...