I sometimes look at it via the metaphor of music.
Playing an instrument vs electronic/computer music.
We do forget skills we don't practice, especially fine motor skills (like playing the guitar or typing code).
There's inherent pleasure in playing a musical instrument - practicing improves fine motor skills and produces satisfaction.
You can play for yourself and that can be a great experience.
Often people create music for other listeners - and now the satisfaction comes not just from your skill, but from how the music impacts your listeners.
They say you can put more of your 'soul' into music made with an instrument, but I'd say there's quite a bit of electronic music with just as much soul.
People who create electronic music don't generate any of those sounds with their fine motor skills, but they do have a plan about how the song progresses and what emotional state it elicits in users.
That's why you have DJs which are more popular than others.
If you stop playing the guitar for a year, then pick it up and try playing something, you will feel very rusty. But give it a week of practice and most of your skill comes back.. and in 1 month you're back to your peak skill.
I guess my point is - If you go full on agentic, you'll loose some of your coding skill, but you can get it back fairly quickly if you go back to manual coding. On the flip side, you get better at using AI if you use it, so your thinking is at a higher level, but you give up understanding the low level details of how exactly the code works.
Either way you're making 'music', albeit a different kind of music.