The Enabling Act was passed by the Reichstag, that was not the president's doing. And while one could argue that the Enabling Act was not in itself a breach of the Weimar constitution, the actual circumstances under which the Act was passed were highly dubious, and almost certainly illegal and a breach of the Weimar constitution. To achieve the necessary two thords majority while also maintaining the necessary quorum of two thirds of the representatives, the nazis had all communist representatives and quite a few SPD representatives arrested, then changed the quorum rules so that only those absent with an excuse counted as absent and then illegally had armed SA present during the actual vote. While the Weimar constituion could certainly had weaknesses that made the establishment of a dictatorship easier, in the end even the somewhat feeble rules that were in place were breached and it seems unlikely that stronger constitutional safeguards would have been much use once Hitler had become chancellor.