One of the reasons is because the big clubs that are accustomed to dominating the Serie A competition are quite slow in updating their players, such as Inter and AC Milan, which have quite a lot of old players as well as Juventus, and Napoli managed to break this domination with a squad list of young players.
Clubs in Serie A do not have large financial capabilities like other clubs in other big leagues in Europe, especially for the English Premier League and also Laliga, thus making big clubs in Serie A more often bring in old players than those who are still young under 30 years old, but Serie A a few seasons ago became quite interesting because the competition for the title was quite tight except when Napoli won which could confirm it sooner, and what was also the cause was COVID-19 which affected club income so that these clubs did not quite aggressively buying players because the funds are limited.
The decline in Serie A overall competitive performance was indeed evident for a period which some attributed to a shortage of quality players and intense competition from other top European leagues. However, the league has undergone a resurgence and teams like AC Milan, Inter Milan, and Juventus have maintained their strong form while others have risen to the occasion. This revival can be credited to strategic investments improved youth development, and a newfound zeal among the clubs. As a result, Italian teams have excelled in recent European competitions showcasing their renewed strength and determination. Serie A current state reflects a thriving and formidable league, poised to compete at the highest levels once again.