Network is a permission on Android, it's just that phone manufacturers and likely Google don't want you to be able to control it. Most custom ROMs, including GrapheneOS expose it properly, often at the install dialog.
It does look like Xposed has successors, but my current approach is to just be selective about installing apps.
I assume they don't expose it to users because once most people start to do that apps would start to implement detections, like if it spoof your location to a certain area then that area will get you "permission denied" error anyway, or I believe some apps do check that if your contact book is empty it assume you didn't give the permissions. It'd become a lot of work to implement a convincing spoof for most permissions to be blocked.
But to be honest, other similar dangerous permissions like "view network connections" and "receive data from internet" are also there, categories are for "camera", "microphone" etc.
I suppose that the average user is more concerned about specific features, and since basically almost all apps require internet it may be there to avoid noise. Still, an "internet" category would have been nice...