[El classico in the Spanish La Liga is an event between two classic sides Barcelona and Real Madrid a very competitive game. Gaining three points from an El classico game is good cause it shows who the better team of the day is but not enough to win you the champions of the league, it's also important to win other games against other teams in the league that's the points you need to win the league so it should be of great importance and not just focus on the El classico.
The importance of the classic is not only in soccer, as you and the previous comments on the subject focus on.
On the sporting side, it is usually the match between the two strongest teams, although it depends on the year, and to win the league you need consistency, regardless of the result of El Clasico, as you have pointed out.
El Clásico is a match between Real Madrid, which is a centralist team, and which was the favorite team of the dictator in Spain between 1939 and 1975 and a team that more or less veiled defends the independence of Catalonia with respect to the Spanish state, and has done so very explicitly in recent years.
This is the crux of the matter. In the political confrontation.