The irony is, that precise argument was used to argue against La Liga's strength, despite dominating European competitions during that time. The criteria just keeps changing to paint the PL as the best no matter what.
Spain's domination began in 2008, months before Guardiola took on the Barça job. In fact the term 'tiki-taka' was invented because of 2008 Spain, not because of Barcelona.
Not being in the Spanish squad of 2008-12 has hurt his reputation. Also he was kind of a liability in his last Madrid years, barely could run and was there on the pitch only to poach goals not unlike current Ronaldo.