It should not be forgotten that El Classco is a friendly match. Therefore, it would be wrong to think that Real Madrid suffered a heavy defeat against Barcelona. Almost all the players changed and Barcelona won 3-0 after scoring 2 goals in the last minutes. This is good for them, of course, but I don't know if it's enough for La Liga, which is a long marathon.
It is acceptable to compare friendly games to actual games for some reasons. During friendly, some players have their one chance performance that could earn them a spot in the starting eleven for league games. It's quite acceptable for coaches to test numerous players and try out new techniques in order to determine the players' true strengths and talents prior to the actual event. You'll be hoping for a victory or at the at least a tie at the end of a game if your side is able to perform similarly to how they did in the friendly games.