As I've said, Poch is a good manager. However, you can make a similar argument for another of Marcelo Bielsa's disciples, Diego Simeone, who has achieved more with an even smaller budget at Atletico (prior to Wanda Corp's recent takeover). In fact, I forgot about Rafa Benitez, whose Valencia side is the only other side other than Atletico to break the Real Madrid and Barcelona's strangehold in La Liga. Benitez even popularized the 4-2-3-1 in the late 90s and early 00s which served as the basis of Spanish tactics over the past decade. Or what about Leonardo Jardim, whose expansive brand of attacking football using the old 4-4-2 and wide wingers took Monaco's youngsters to the Ligue 1 title over PSG and almost to the brink of European success? These guys, alongside Poch, are all really good managers.
However, Mourinho, Guardiola and Klopp are on another level; they redefined modern football. There are literally books written about them and their tactics. Mourinho almost killed off 4-4-2 and his defensive tactics is now copied almost everywhere. Guardiola pressing, possession and six-second recovery rule served us with some of the best attacking teams and most dominant in recent memory. Klopp's gegenpressing, lightning transitions and hunting in packs can elevate weaker teams to the level of far superior ones. In years to come, these three will be treated with the same kind of reverence we do now for Arrigo Sacchi, Rinus Michels, Valery Lobanovskyi, Johann Cruyff, etc.