This is not age. Basically you stopped doing deep work (programming and learning) and move into doing shallow work (emails, meetings ,etc). But this a natural s

This is not age. Basically you stopped doing deep work (programming and learning) and move into doing shallow work (emails, meetings ,etc). But this a natural step of promotion. The problem is that the shallow work now occupy most of your time, and since you are not doing deep work, you deep skills decay. The decay created a gap between what is expected from you, and what you are current level is. Another issue is the great acceleration of new tools / new tech , which occur both in breath (a lot of new tools) and depth( each tool is more complex). This acceleration contribute to the imposter syndrome, since you do not invested enough time to become expert in the new tech. I.e. you were promoted based on you skills with the old tech. What you must do, if you want to close the gap, is use your free time to do more deep work.