Personally I think Ancellotti is hugely under rated and probably doesn't get mentioned in the same breath as Klopp or Guardiola, although he deserves to, because as you say, he doesn't have an ingrained style of football that he insists on playing.
I reckon that he would also be a very successful national manager because of this, more so than the other two, and if he were to replace Southgate as England boss,
I would immediately have them as favourites for the next tournament they are in
apparently the FAI turned him down last week