I agree with you. One of the reasons for Brazil's poor performance is their coach. 62-year-old Dorival Junior is not an experienced coach. He previously coached Sao Paulo and Flamengo. Brazil is a renowned team. As their goal was to do well in the World Cup and win the Copa, Brazil needed a more experienced coach. Also I saw Brazilian players ignore Coach Dorival. They don't give enough respect. However, this could also be my misunderstanding.
Brazil should definitely try to strengthen the bonding between the players. Because there is no shortage of talented players in Brazil's squad. If the chemistry between the players is good then this team will be strong.
I understand the importance of having a young and vibrant couch especially in a team like Brazil but this can not be justify as one of the reason for their irritating performance. Brazil performance was not only poor, it was very embarrassing and insulting for a team that have produced famous and talented players in the history of football and are also known for taking sports activities very serious to end up playing the way played in a tournament as serious as Euro. I don't know much about their couch but even if he's less experienced as you pointed out, the players can adjust while in the pitch to make things work right. Majority of their squad players play in a very recognized clubs and have experience to play even without the instruction of a couch. What I could figure out from their overall performance is lack of dedication. They were playing like people who weren't interested but forced to come and participate. The couch should be relief from the duty because at that age, nothing much is expected again.