I notice this already after around of 6 months heavy usage. Skills decline, even information gathering etc

I think it is more accurate to say some skills are declining (or not developing) while a different set of skills are improving (the skill of getting an LLM to produce functional output).

Similar to if someone started writing a lot of C, their assembly coding skills may decline (or at least not develop). I think all higher levels of abstraction will create this effect.