While I certainly see you point, there is no reason why the at-home-work that students need to do in a flipped classroom should take any longer than the homework a student would receive in a typical classroom. If the work is a reading or a video, students can work at their own pace, which is often faster than a typical classroom, you can skip/speed up parts you already understand instead of having to sit through a redundant review lectured by your teacher. But - you're right - it does take a certain level of dedication from the students; just like so many students who get As in high school and fail college because they don't have the parental and teacher structure checking in on students as much.

I see education as having 2 main parts:

Learning skills/information

Practicing those skills/seeing how they connect to previously learned topics and skills/their implications on everything else you've previously learned.

I think it would be much easier to perform the first bullet on your own using electronic and other resources. The second bullet has so many facets/permutations/opportunities that it seems like it would be best done as part of a collaborative effort.

Also, in a typical classroom, a student who doesn't understand a topic is often tasked with learning the confusing material on their own. In a flipped classroom, a student who doesn't understand a topic they attempted to learn independently can ask a trained teacher for help; the whole point of a flipped class is to allow the teacher more time for differentiated activities.