Is knowledge of the past no longer useful for us today?

This is not true because past knowledge is always helpful in any situation. Everyone learns from experience and people use that past experience to make sure that they don't make that same mistake they've made before. Am example is if someone scores poorly on an exam that was very important. Maybe they just didn't study or wasn't really serious about it. They should learn next time to study or actually put effort into their test so that they won't score poorly. Past knowledge is always an upper hand to have in any situation.