Barcelona and Real Madrid each have one of the best players of all time backed by world class players with massive fees and massive salaries. Oh and they have turnovers €250m higher. So we can't sign a Ronaldo, Bale, James or whoever in the first place, and subsequently we don't have the draw to sign additional top class players. I'm talking about the category and draw that those two clubs have. The only way around it is PSG, City or Chelsea money, and even then they don't have the same appeal for player. Serie A has reduced appeal. Bale isn't coming here. James isn't. Not even Modric.
BTW Real Madrid had a bench of Casilla, Varane, Arbeloa, Kovacic, James and Jese in the last game, but I know what you are saying (applies more to Barcelona). With our injuries we'd be in trouble, but they have Ronaldo or some other guy to bail them out in most games.
So we're having to do what the PL clubs have to do - sign young players who have the potential to be big stars. But then Pogba and Dybala eventually end up at Barcelona, so what do you do to combat that? We need to generate more income, continually win trophies inc. CL, somehow keep hold of our players, improve our youth system so we can pad our squad with youth products and spend all our money on 1-2 players each season. It took Barcelona 10-15 years, the decline of Serie A, Ronaldinho, Messi and his supporting cast to become the desired location to play football.