It's not a failure if a team fails to win a trophy in a season. Madrid is actually having a bad playing season but it is often said that not everyday is a Christmas. There won't be joy in watching football if one team keeps dominating over the other teams season in and season out. Madrid however still has a chance in UCL despite their bad form, winning over Chelsea will not be that difficult for them.
Real Madrid fans will disagree with you. It's not like any team can rely onley on their history and still be successful. What fans wants are good results beside consistent performance and entertaining gameplay in every match. Of course there will be ups and downs along the way but we didn’t see that with Real Madrid this season to be honest.
Unfortunately this season has been a failure for Real Madrid and I can explain to you why. Despite having some of the best and most experienced players the coach Ancelotti couldn't create the right team dynamic to perform well, even against smaller teams. On the other hand, Barcelona, with Xavi as their coach, who lacks experience, and a young and inexperienced team managed to defeat Real Madrid and is on their way to winning LaLiga and Copa Del Rey after winning the first leg against Real Madrid.
Therefore it is evident that this season has been a disappointment for Real Madrid and it could get worse if they lose early in the Champions League against Chelsea.