The season after they lost the final they still perform in CL.Remember they knock the mighty arsenal out of CL(That time Arsenal was the master of EPL,like Chelsea today).They lost to Inter on away goals.Still they play the best attacking football ive seen from Valencia in the 2nd leg match against inter.
True after that season they dont perform well in CL.Not just in CL, they also dont perform well in liga,Yes they win the liga,but with small numbers of goals(Baraja being the top scorer),They draw more than they win.That season real was the only contender for Liga title.Barcelona was crap.Later Benitez leave the club.Then Ranieri came, then Flores.

What im trying to say is Valencia is not the team they used to be.The days of Hector Cuper & Benitez have long gone.Thats why they dont perform.
But im optimistic that they will perform next season,in Liga & CL.