TL;DR: the debate around Acqua di Gio isn't really "good or bad perfume," but rather "overexposed or overrated" — a distinction that comes up often among enthusiasts who clearly separate the two.
A perfume that became so popular it divides opinion
Since its release, Acqua di Gio has become one of the best-selling and most-worn men's perfumes in the world, alongside a handful of other universal best-sellers. This omnipresence has a paradoxical effect: the more a perfume is worn, the more some enthusiasts grow tired of it and see it as "unremarkable," regardless of its actual quality.
"Overrated" or simply "overexposed"? A distinction that changes everything
One point comes up regularly in connoisseur discussions: the distinction between a genuinely overrated perfume (whose quality doesn't justify its reputation) and a merely overexposed one (that you get tired of simply because you smell it everywhere). For Acqua di Gio, much of the criticism falls more into the second category than the first.
What critics complain about most often
The most negative reviews describe a composition judged too simple or too "clean," evoking for some a cleaning-product smell rather than a sophisticated perfume. This is a fairly common complaint about the very marine, mineral aquatic compositions of that generation.
Why it remains a classic for many, regardless
Conversely, many enthusiasts keep a particular attachment to this perfume, often tied to a personal experience (first perfume, a memorable period) rather than a purely technical analysis of its composition — a common phenomenon for perfumes that marked an entire generation rather than a small circle of connoisseurs.
Should you try it despite the controversy?
The only way to decide for yourself is to test it directly: its reputation as a "basic" perfume or, conversely, a "timeless classic" depends almost entirely on your own expectations and your personal exposure to this very widespread olfactory profile.