Serie A is one of the best leagues in the world and yes there are many strong teams.
Serie A is one of biggest leagues in Europe and the world of course but its position has been decreasing a lot since 1990s especially since 2000s. The scandal Calcipoli in 2006 makes things more worse for Serie A. Nowadays, it is not easy to find top-notch players in Serie A from goalkeepers, defenders to attacking players.
Back in 1990s and 2000s, Serie A was full of star players and many transfer records were made by Italian clubs which nowadays can only be found in La Liga, Premier League or Ligue 1.
If we look at the example you mentioned in terms of Inter, if they join the European league, better quality matches can be watched in the European league. In my estimation, in a few years the European league will become an important tournament, at least like UCL. We see very big teams in this cup this year. Teams, most of which are at the UCL level, compete in the UEL. Of course, Inter could be one of them.
They must focus on internal resources, start with youth academy. With limited finance and attraction, they must have good home grown players and use them to improve clubs and league performance then ranking in Europe. Later they can become a more attractive destinations for star players and they can become a great league again.