The people who can't code any longer are still typically able to describe an algorithm, at least in pseudocode.

Whiteboarding Yet Another Graph Search Problem With Perfect Syntax[1] might be beyond their current short-term abilities, but I'd be surprised if they couldn't produce pseudocode and architectural design that solves most real-world problems.

On the other hand, there are plenty of "seniors" who couldn't write code in the first place.

[1]Everyone knows which employer does this.