The problem with Brazilian teams is that the country's coaches have outdated philosophies and are tactically much inferior to European coaches. Just watch the Brazilian national team's games and you will see that the team does not even have a tactical scheme. There are many deficiencies, especially in positioning, which have been happening for years.
Then what prevents the Association from hiring a good foreign coach? BTW, Brazilian coaches are very successful across the globe. The rot is much deeper and in many cases coaches are just convenient scapegoats. The quality of Brazilian football has gone down, both in terms of international matches and club matches. Most of the players are migrating to Europe and the middle-east, as the local leagues doesn't have required quality. In the end, this contributes to the never ending decline in terms of quality.