So with this stance (ie. against "side-loading" - what a crappy term) not only you make things worse for everyone (not being able to use their own devices as they see fit) even though they wouldn't be visiting China, you also validate region locking (another shitty practice that has no place in a global internet and only serves whoever wants to divide people) including any tech necessary for it (and thus monetary incentives for whoever implements it) and not solve the issue at hand (people being forced to install malware) since it can be done just as easily through normal routes.
No, if you do not want such stuff then speak against it and do not put yourself in a position to be affected by it (do not visit China, use burner phones, whatever).
Perhaps it is more illustrative to compare it with physical stores. The Google Play Store is one store, F-Droid is another well-known one, and there are others. Allowing only Google to install apps on your device would be like allowing people to only buy products from a store controlled by the producer of the product, reasoning that other stores might modify the product. If cheese was solely a Dutch product, the Dutch producer would get to prohibit Americans from buying cheese at stores other than a single Dutch chain, with no oversight of the American government (such as the FDA) for fear of product manipulation. They might infect it! Bringing it back to Android, I (a Dutchman) would only be allowed to get my apps from the Google store which is within some foreign jurisdiction.