European soccer has been at the top for a long time as not only there is a very high interest in the game but a lot of money is invested by the owners of the leagues, this may give the impression they are stagnating but when you are at the top there is nowhere to go but down, the rest of the world is catching up as they send their own players to Europe and they play against the very best, but without a strong domestic league it is difficult to see a team other than Argentina or Brazil being able to win a world cup to those European teams.
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).