I don’t have too much experience with coke users, but plenty with alcoholics over the decades.
I bartended my way through college, so spent lots of time with the weeknight drunks who were there every day. Plus I had a few in the family.
And I noticed that after a certain age, or a certain number of years in the grips of severe addiction , it stopped mattering if they were drinking anymore, their brains were permanently fried.
There just isn’t going all the way back after a certain point, even if you quit drinking. You will be slower, and stupider, and repeating yourself forever. Your fun-loving, party personality from early drinking never comes back. You are dull, boring, and slurring even when sober.
That’s not counting the other physical effects of long term alcohol abuse.
Grim stuff.