Maybe if you just look at the table, you can say that since Atletico is in third place, everything is not so bad. But I remember Atletico well from the time when they played with Real in the Champions League finals, naturally I do not compare their average indicators with the worst seasons, but compare them with the best.
Well, for a decline I would compare their indicators by year, so it would have to go from best to average to worse, and just on placing and games, they did a better season last time than two years ago, if we count just the first half, it was one of their actual best so rather than a decline as I said, I see this as a continous failure at improving but without major succes nor major disspointments, let's be honest here even their fans don't expect them to be on pair with the top two.
Yeah, they had a good run between 2017 and 2021, but let's look at 2018 when they placed second, Real was beaten that time 12 times!!! ,in the next two years, even added Real and Barca never lost that many games!
I always considered Atletico going above the 3rd a fluke rather than a performance, probably a biased view, but that's what I always thought of them