Athens works well for
History and culture travelers (the Acropolis, ancient Agora, and several major museums), city-break travelers wanting a dense, walkable historic center, and anyone using Athens as a base for Saronic Gulf island day trips (Hydra, Aegina, Poros are all reachable in a day).
Athens is a weaker fit for
Beach-only travelers — Athens itself is a city, not a resort destination, so if a beach holiday is the actual goal, the Greek islands (not covered by this pilot yet) are the better fit. Travelers wanting a quiet, slow pace, since central Athens is a busy, sometimes chaotic capital city.
How much time to give it
Two to three days is enough to see the major sites without rushing. Longer than that only makes sense if you're using Athens as a base for day trips rather than staying in the city itself the whole time.
If ancient history and a walkable European capital genuinely interest you, Athens delivers well. If you're dreaming of white-sand beaches, treat it as a short stopover before the islands rather than the main event.