Yes, agreed.His tenure with Ajax, Netherlands and Barcelona will make him one of the most influential people in football. An influence still felt today.
IMHO, Michels and Clough are the two greatest managers in football — though for very different reasons.
The difference between managers who win things, and managers who win things and leave some sort of legacy/style is an important distinction.
As an example, Ferguson was a great manager, winning trophies galore with 3 rebuilt sides but his legacy is, I think, only left for the PL or even more specifically, Manchester United. But the absolute greats change the way we think about football.