UEFA still has the best football leagues in the world. No other leagues can match competitions such as English Premier League, Spanish La Liga, Bundesliga, Serie A, Ligue 1 and Eredivisie in terms of quality and popularity. I would say that if you take the list of top-5 football leagues around the world, all of them would be from Europe. And this has helped the European players enormously. They get the experience by playing against the best players in the world. But now, UEFA clubs are increasingly diversifying their squads, by adding players from all around the world, including those from CAF and AFC (in addition to UEFA and CONMEBOL).
That is true but European leagues are not the same thing as European national teams. Clubs in the European leagues have a lot of money and with that money and great infrastructure they attract the best players from all around the world. National teams are different because they can only take players from their nations. There are few exceptions where a player can join another nation's team but those are exceptions. However, like you said, those top European leagues give players the opportunity to constantly play football at the highest level. For example, s good player will improve his performance if he is playing in England. While the same player will probably stagnate if he plays football in some minor league.