My biggest mistake when referring to RM's history was when I mentioned the 60s. It should have been 50s instead and I corrected it. I'm very well aware of their history and they are indeed the most successful club ever. But they also won most of their European titles in two eras, I think it's fair to name them the Di Stefano era and the Ronaldo era. Add the "Galactico" era and you have 12 of the 13 EC/UCL titles in periods that put together sum only 15 years, divided in periods of five years each (1956-1960; 1998-2002; 2014-2018).
Outside of this highly successful stints, they had a period of 37 years where they won it only once, and the most recent drought of 11 years between 2003 and 2013.
Point being, even Real Madrid, the biggest club in the world, is subject to circunstance. And yes, even for Real Madrid standards, 4 European titles in 5 years is overperforming, specially when it's so clear that without one player in particular they might not have won a single one of those.
Now, don't get me wrong. I never said Real or Barça are bound to become "average". Nor have I said Real won't rebound from the hardships of their post-Ronaldo transitional season. What I'm implying is, both clubs won't have the edge that they had over other top clubs in Europe in the last ten years. They will remain great clubs on their own right and might win the UCL in a near future, but that edge will be removed. So, forget past results for a moment, do you have anything to suggest that in the next ten or twenty years the Spanish giants will have the same level of success as they did in the last ten or twenty? I think not.