Can the aforementioned Hadith be considered evidence for excusing ignorance, given that it states that "there is no god but Allah" saves from the Fire a people who know neither prayer, nor fasting, nor charity, nor rituals?

The aforementioned Hadith is authenticated by Al-Albani. It is a prophecy from the Prophet, peace and blessings be upon him, about what will happen to the Ummah in the End of Times: the spread of ignorance, and the persistence of some in adhering to the word of Tawhid (monotheism). It contains evidence for excusing ignorance for those who lived far from knowledge and scholars. The Imams have agreed that whoever grew up in a place where knowledge and faith were scarce, and was new to Islam, and then denied an apparent, widely transmitted ruling, is not to be excommunicated until he learns what the Messenger brought. It is stated in the Hadith: "A time will come upon people when they will not know prayer, nor zakat, nor fasting, nor Hajj, except for the old man and the old woman who say, 'We found our fathers saying La ilaha illa Allah (there is no god but Allah),' while they know nothing of prayer, nor zakat, nor Hajj... He will save them from the Fire."