What are the matters agreed upon by scholarly consensus, regarding which no one is excused for being ignorant of them or for not seeking them out?

It is not possible to enumerate all the issues for which ignorance is an excuse or not. However, there is a general principle that encompasses them. All scholars agree that ignorance is an excuse, but they differ on how to apply it and on the specific issues for which it is an excuse. This makes reaching a consensus on the details of this matter difficult, even though they agree on it in general.