Athens is an incredible place, I basically don’t recognise this description. Sure, if you go to the wrong places it’s full of overweight Americans on a cruise (like if you only go to Leicester Square etc. in London), but Athens has a legitimate claim to be the coolest city in Europe (taking over from probably Lisbon over the last 5-10 years which took over from Berlin). And not just as a budget destination, 3 of the world’s 50 best bars are in Athens this year, that’s one less than London and New York on the list which are the joint leaders.
Istanbul is a truly great city too, of course, but they are just very different.