Bro I don't compare La Liga teams with Serie A teams. I know other teams in La Liga other than Barcelona and Real Madrid don't spend a lot of money building squads. Madrid and Barcelona spend a lot of money and are two of the best teams in La Liga. But there are many teams in the Premier League who are very rich and spend a lot of money. Manchester City, United, Liverpool, Arsenal and Newcastle are very rich clubs. And the Serie A teams will be far behind these clubs financially.
Actually your opinion is not wrong because indeed transfer activity in Serie A is lower than other leagues
But the quality of players in Serie A is not too bad even if they don't spend a lot of money
Inter who managed to go to the champions league final is an example.