How to deal with professors who don't respond to emails?
I cannot give an Asian perspective, but the situation you describe was quite common in many universities thirty or more years ago, at least in my country. Students were not supposed to have rights, and many professors would simply ignore most of the students queries or requests, whatever the medium used to deliver them (emails were not so common in those days). And the situation was even worse in the humanities where I had some friends (and I've been told that a few bad habits have survived to the present).
Since also the university was unresponsive to complaints, the most common solution at the time was to ambush a professor at their department, frequently sneaking into the department (since one wouldn't know when the professor was in, students would sometimes take turns to avoid missing them). Indeed, this is not a fix to the problem: it's just a survival strategy, which would hardly work and be recommendable in these COVID-19 times.
I'm afraid, though, that alone you would not be able to do more then the above survival strategy. In my experience, the only thing that works—at least partially—when a university shows such generalized level of unresponsiveness is when students unionize en masse and make a strong action (common actions are occupation of the university, contacting media and such). Indeed, the possibility and the chance of success of such an action depend on the political climate in your country, in the willingness of all students to participate in such an action and in the possibility of finding a strong leadership within the union.
A base action, suitable for these unlucky times, would be that of preparing a document describing the problems, and signed by as many students as possible, to be presented by your representatives at the class meetings. The representatives should go well prepared and should be able to choose the right time to present the complaints (in my experience, students frequently miss the right moment and are frequently out-of-phase with respect to the agenda of committee meetings). Send your document also to the Dean and, possibly, also to the media, finding someone who would be willing to side you and follow your cause if nothing happens. Indeed, before doing any of the above, you should estimate the probability of success on the basis of your knowledge of the situation, the chances of retaliations for those involved and whether it's worth it, taking also into account the time that doing all this would take: pick your battles carefully.