Moving from senior individual contributor to managing a team is usually described as a switch from technical to people work. In my experience that framing is wrong in a specific and costly way.
The technical judgement did not become irrelevant. It stopped being used to produce the work and started being used to make decisions about the work: what to attempt, what to defer, which risk was real, whose estimate to believe.
What actually changed
The unit of output. Yours is now the team's, which means the fastest path to a result — doing it yourself — is usually the wrong one, and knowing that intellectually does not make it easy.
The feedback delay. A bad technical decision shows up in hours. A bad people decision shows up in months, by which time the causal link is easy to miss and easy to rationalise.
What is not delegable. Context is not delegable. If you understand why something matters and the team does not, no amount of task assignment closes that gap.
The thing worth protecting
Enough hands-on contact to keep your judgement calibrated. Not to be the best engineer in the room, but because leaders who lose that contact start making confident decisions with a model of the system that quietly went out of date.