I think it’s undeniably true that money talks and the EPL has more money and this affects the league’s quality. But I also think two other things may be true:
1. No EPL team is as attractive for the very top players as Real Madrid, Barcelona, and Bayern Munich are. Those teams can pay as much as top EPL teams, are always *really* good teams competing for big titles, and are storied clubs. There’s no EPL team that matches that. Manchester United is storied and can pay, but their lack of recent titles makes them less attractive in recent years, I think. Man City has the money and recent success but isn’t a storied club. Liverpool sort of ticks all the boxes, but is just not quite there in all three areas. Same with Chelsea. What this means is that we’d still expect a lot of the *very* top players in the world to end up not in the EPL, because there’s a few teams that are generally even more attractive destinations than any EPL team is.
2. Leaving aside very top players that go to RM/Barcelona/Bayern, the EPL’s money will allow many of their teams to largely get the pick of the litter otherwise. However, it may be true that the pick of the litter isn’t necessarily meaningfully better than the players who are left out of EPL money—especially when we take into account that teams picking transfer targets don’t know exactly how good someone will be in the future. For instance, to use a simplistic model, let’s say an EPL team can use their money to pick a set of players that people think are an 8.5/10 in quality. And let’s say a La Liga team can’t get those players because they can’t pay EPL money, but maybe what they *can* get instead are still players that people think are an 8.0/10 in quality. That’s not a huge difference, and it becomes even less meaningful when those 8.5 and 8.0 numbers are just projections—the 8.5/10 EPL team could end up being a 7.5/10 team in reality, while the 8.0/10 La Liga team could end up being a 9.0/10 team in reality. So IMO what the EPL gets are basically players that are *projected* to be *a bit* better than the players other leagues end up with instead. On average, that’ll pan out into a stronger league (since players projected to be better will, on average, end up at least a little bit better), but it won’t necessarily be *a lot* stronger.
If you combine these two things, you get a league that is still likely the strongest, but maybe not way stronger (despite having way more money), and with top teams that still may not be as good as the very top teams in other leagues.