1. Fewer number of clubs can win their respective league now, compared to 40 years ago. Same clubs winning/competing for the league title every season.
2. Only about 3 clubs maximum each season that are capable of winning their domestic leagues. ie. Clubs from the 'Big Leagues' (Spain, France, Italy, Germany & England)
3. Champions League money affecting 'smaller clubs' playing a strong team in the domestic cup, prioritising European qualification.
4. Champions League seeding. Set up to aid the 'bigger clubs'.
5. The rich are getting richer. The poor are getting poorer. In modern football,
money rules.
Net result:
More Clubs achieving 'The Treble' in recent years.