Homework should be there to show mastery and reinforce learning, but more often than not, it ends up being just busywork or silly arts-and-crafts type projects. Also, we need to get rid of school-day “fluff” (e.g., pep rallies, homecoming and school spirit nonsense). Students need more - rather than fewer - opportunities for real learning during the school day.
I’m not sure how I feel about “flipped” classrooms (where the kids watch lectures and/or videos at home and the classroom is used for working through problems with the help of the teacher). Done well, with dedicated teachers that engage with all of the students at their individual levels and are there to help them master concepts, it is a model that can work for some subjects, particularly in science and math. In other subjects (humanities, for example), having smaller, seminar-style classes wherein all of the students are expected to contribute to discussions, it becomes patently obvious whether or not students are doing the readings and are able to participate.
One solution would be to have a longer school day - with NO homework; another would be to have a longer school year or have school for 6 days a week rather than 5 days, again with NO homework, A longer school day will never happen because of sport practices and games; the latter two possibilities will never happen because nobody wants to lose their weekends or summer vacations.