The conductor as a wanna be composer

Also Kletzky
de Sabata
Marinuzzi
Skrowacewsky
Kubelik
also today: M.Tilson Thomas
Salonen
Maazel
Previn
Serebrier
Segerstam (as prolific as Haendel or Vivaldi)
A case apart was Igor Markevich, initially a young prodigy composer much in the roots of Stravinsky; later avoiding composition.
the list could be long, almost endless.
In my much- less- than- good English I would raise the following topic/problem.
As far as conductors-composers of the past are concerned , we can more easily judge them as primarily conductors, because their legacy as composers (albeit appreciable or good) has not reached "in the common opinion" the status of "great".
But today ? The situation is not so clear.
For instance the Boulez case (I would consider him primarily a composer) is akin the Previn's case?