Developmental indicators like HDI, childhood mortality, access to clean water (not a right in Italy until 1996), etc.

If Italy in the 1990s was a developed country, then a lot of countries treated as "developing" today are actually developed, hence why I gave the examples of Turkey, China, Malaysia, Serbia, Russia, and Thailand - countries that are "developing" yet have sustained developmental metrics comparable to Italy in the 1990-2005 time period.

Italy was added to G7 (then G6) in '75!

G7 was created by the then 7 largest Oil importers in the aftermath of the 1973 oil crisis. While it has connotations as a developed countries group, the reality is that Italy's developmental indicators lagged compared to much of Western and Northern Europe until the 2000s.