when i was younger, we didnt have cellphones. i had ~20-30 phone numbers memorized, at least. i also used to remember my credit card number. my brain has not deteriorated now that i have offloaded that to my phone.

point being: it depends on how you use it. if you offload critical thinking to ai, you will probably (slowly) atrophy your critical thinking muscles. if you offload some bullshit boilerplate or repetitive tasks or whatever, giving you more time overall to do the critical thinking part, you will be fine.