I DO NOT think it should be used for nonquant subjects, and I see how it would be a disaster for students with different learning styles.
I run a partially flipped humanities classroom-- they read and do a limited amount of A/V viewing/listening work outside of class, and are held responsible for that material when we do discussion-based activities in class. This is not the only way I teach, even within this class I change it up a lot, but it's one tool, and it works really well for the particular population I teach.
Nobody should be forced to flip a classroom who prefers teaching another way. Nobody should feel like if they "flip" some aspect of the course they have to do the whole thing that way. Nobody should be put in a position to change their teaching methods without (informal or formal) professional development to support that change.
There is serious professional development involved in doing this well-- in designing a course well, not just in "flipping." IMO there are a lot of people who are assuming that the answer is the delivery strategy, when really the answer is having sufficiently trained teachers who CAN CHOOSE the right delivery strategy for their particular students and material, and who CAN ADAPT on the fly when something doesn't work for a particular student.
The folks who are looking for the answers in tech are just getting it wrong, IMO. The answer is in the teaching. My two cents.
