Real Madrid's reign didn't feel as long as it was because it was never a reign to begin with.
As much as Madrid fans try to pretend that the past 5 years were fantastic, the reality is that in the seasons where they won the CL, they were the laughing stock during most of the year. Madrid never played well, and it was always a bore to watch. Watching Madrid felt like an ugly chore even for the fans.
They regularly got humiliated in the league and the cup, which took up most of the calendar. Not only that, but even in the CL, they never won convincingly. They either needed massive refball, massive amount of luck, or both, to get past any and all ties. The only league title they won was tainted with massive amount of refball, so notorious that even coaches called it out.
The fact is, they never even won a treble, whereas Barcelona did it in that season when Madrid didn't even win the CL. That is why, whenever they say "4 CLs in 5 years", there it is, Barcelona's treble standing in there, like an ugly pimple in a cute face, one that really hurts.
What's worse, they never got a hold of Barcelona. They lost so many games against them, that for the first time after 87 years of domination, Barcelona went ahead of them in all-time wins. Not only that, but they lost humiliatingly and embarrassingly, home and away.
During the golden age, Madrid fans only got to enjoy the week after winning the CL, only to start suffering again all year. In the end, the implementation of VAR put them in their real place: out of all competitions by early March. They won their very own treble: knocked out of the league by Barcelona, knocked out of the cup by Barcelona, knocked out of the CL by Ajax, all in a week, all at home.
So much for the golden age of Madrid.