I agree with all of this - and the skill that leaders need isn’t demonstrating (intermediates can do this), but coaching - this will help develop the team to be able to solve the issues themselves.
You can’t coach what you don’t know. And the reality of leading an engineering team is that when your team members actually seek your opinion on a problem, you have to know the specific solution to specific details, not general patterns.
But as a leader, if you don't know - then it's an opportunity for you and the team members to learn it together, the real point of which is teaching the team members how to adapt. Half the crap people ask me, I don't know, but I'm happy to find out with them. And maybe next time they'll be able to figure it out on their own.
And while you are fumbling around trying to learn the technology, the market is leaving you behind, you’re burning through resources and you’re not creating business value by either making the company money or saving the company money.