Only terrible calculus teachers/class setups don't respond to student questions. Until you can do the same thing with a video there is going to be a gap. Traditional collage classes are generally based on the idea that ~1/3 of the time is synchronous learning in a classroom with a teacher 2/3 is self study. Have a 3 hour class expect 6+ hours of homework / projects on average. With that said, most classes don't spend a lot of time on questions, but they occur at the right time as in right in the middle of a lecture or right after it.

Presumably online videos could let you cut down on some class time, but even 1 hour after watching a video your going to forget some of your questions and much of the context of other questions you remember.

PS: If you took calculus in a setting of 500 people where you could not ask questions you still got ripped off even if there was a teacher in the room.