Then class time is reserved exclusively for doing the assignments. No phones or computers allowed.
But seriously, teaching in public schools these days relies so much on technology, youtube, that it makes no sense to have teacher’s as paid professionals, just get subscriptions to technology services for the kids and teach them how to work them. I think we still need places to socialize kids, but that’s a different job. Anyway, yes, too many teachers are simply there to enforce unnecessary social hierarchies and rigid modes of thinking, there is no need for most of them.
If we're talking about K-12 education, that is for everyone and it's in society's interest that the most people learn the fundamental knowledge that we are trying to teach them.
I'm certainly open to the idea that our current approach is not optimal but I'd need to see evidence that a seminar-style approach would work in that setting. Maybe for some high school subjects. In fact some English classes were that way. We'd get a reading assignment, and then discuss in class, and then typically also have to write something about it on our own.
But math, sciences, and English topics such as grammar were all taught by lecture and example and I'm not sure the seminar approach would work as well there.