What a past history has to do with what's La Liga today. 15 years ago Atlético just ascended from second division. They have been selling best players for long time after that. Torres, Agüero, Falcao, Costa and many others. That's not any longer the case.
If you dig even deeper in history of La Liga you will see that in the 70's, there was just one big team, Madrid and two much smaller, Barça and Atlético.
But things aren't set in stone. That's not how Spanish see things imo.
If you check last 5 years, you will see 3 les for Barça, 1 for Madrid, 1 for Atlético. They have been 1-2-3 all five seasons. In the last 5 seasons Atlético also made two Champions League finals. I don't mention they won the Europa League, because unlike the old UEFA Cup that way very hard to win, it's a second rate Cup.
Barça has a great team, their budget is huge. But it's absurd to think any coach can win them the league. Pep and Luis Enrique are world class managers.
Tell me, who brought Dembele or Coutinho, who sold Neymar? Valverde?