They do!
People follow their clubs, and often cheers on every win. Don't listen to anti fan or any of those disregarding certain cup because they can't win it.
Of course there are heavier, high prio trophies, and team has to set their priorities, and because of the differences in levels you might thing they careless. Similar to lower rank clubs during the leagues, earlier matches in CUPs are often boring.
Everything is subjective, If Liverpool lost to Chelsea in Semi-final of Carabao cup, well trust me it hurts them even higher than in EPL.
Barca is still winning their domestic cup and Real just couldn't, they just failed. They won lots of CL but they fall flat in domestic cup and La Liga against Barca. Because they careless? NO, they just couldn't beat Barca in La Liga and choke in one of two game in Copa Del Rey. (this is the same reason I never agree to say Real dominated Europe, they got owned in Spain, time and time again).
Are they still relevant in 2020. Have they lost the glamour?