I wouldn't overstate this. These days the Spanish, Italian, German and, to an extent, French leagues are much more competitive than they were, say, a decade ago. There's a reason that transfer windows now are full of bids of £60m for far-from-proven prospects rather than the Premier League swooping for Europe's best like years of old.
Could Man Utd etc. afford to spend £100m on Europe's best players? Sure. Would said players jump at the opportunity when they could get the same in Serie A or La Liga? Quite often not.