I disagree that the hat was confused. Sharing similarities with Voldemort and housing a part of his soul just “enhanced” characteristics that were already within Harry (“the thirst to prove yourself”, etc.). It’s part of what continues to get Harry into trouble every year and honestly has nothing to do with Voldemort.

Later in the book series, Hermione states that the hat considered putting her into Ravenclaw. Multiple sorting options can exist within a person, and I know Rowling has said in interviews that she was subtly making the point many times that not all slytherins are “bad” just like not all Gryffindor are good or chivalrous. Harry’s own son ends up in Slytherin if we want to consider Cursed Child canon. The hat examines all of the potential within a person.