“Perhaps by his era there were no longer such spiritually inclined people; or there still were, but the special siyata dishmaya (Heavenly assistance) that allowed them to pray 9 hours a day was withdrawn???”
They didn’t spend nine hours on davening because they had siyata dishmaya. They got the siyata dishmaya because they spent nine hours on davening. The reason why the chassidim harishonim stopped existing is not because the siyata dishmaya was removed, but rather because people stopped spending so much time on davening. therefore, it stands to reason that even nowadays, if one spent extra time on davening then they would in turn recieve extra siyata dishmaya throughout the rest of the day.