I believe the first really big wake up call was when Brazil got destroyed when they hosted the World Cup in 2014 against Germany. I don't know the data, but it must have been the worst defeat in decades for them? Losing a game 7-1 when you host the World Cup as the biggest football nation of all times is like red alert.
2014 world cup at home was really the peak of brazilian soccer decadence personified on the match they lost by 7x1 against Germany. However, the decline started in the world cup of 2006. Brazil was the favorite, but failed to manage beating France on quarter finals, if I remember correctly, with the goal of Thierry Henry.
From that world cup on, everything has fallen apart for Brazil in soccer. Even Neymar, idolized by a vast number of fans globally, wasn't enough for Brazil to retrieve its glory.
A new composition is needed in brazilian national team. To start playing as a squad and to stop idolizing one player or another should be the first step. The reinforcements yesterday from Botafogo was decisive for the victory against Chile. And both Botafogo' players, Igor Jesus and Luiz Henrique, were unknown players for majority of the public.
I'm pretty sure there are others like them. It's the objective of the scout team to find them, just like Botafogo is doing, and adding great value to the club's performance.
I think is not all that simple to identify an exact point in time as the beginning of their decline. Frankly, only counting titles would not be appropriate as winning it is incredibly hard. Back in 2010 the Netherlands played an incredible game and their team was impressive with Snijder and Robben and van Persie, etc. In other words, it is fine when you lose a game against such a high quality team. It can happen to anyone, Brazil included of course. But the 7-1 against Germany was a shocker for me.
You could of course go back so far and mention 2006 as well, but France has indeed been a very good team, too. But the decline that you could now recently observe is taking place on a different level. They can barely beat the South American underdogs. If it wasn't for so many ranks to qualify from South America for the World Cup, I would still be hesitant to say that they will make it. Now with these conditions they will make it, but they are not playing like any Brazilian team from the past. They are losing more than 50% of their games and without disrespect towards all of those great South American players, Brazil has been above anyone else along with Argentina for a very long time.
But as always when the real games are around the corner, I still think that Brazil is able to beat a lot of other teams when they are in good form.