Serie A was clearly one of the strongest leagues in Europe before their overall league competitive performance began to decrease. We had AC Milan, Inter Milan, and Juventus, among others, who were all in excellent form and consistently dominated European competition. All of these teams are still performing well, and there are more on the way who have been excelling in European competitions. I'm not sure what caused the league's general performance to fall; might it be a shortage of quality players, as it was previously? But I love the zeal currently in the league, and they're doing better than ever, as evidenced by how most Italian clubs performed in European competitions they participated in last season.
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.