How much does it really help you if your complete user-space can still be messed up by an offending Windows SYSTEM process? As I understand it, they are able to

How much does it really help you if your complete user-space can still be messed up by an offending Windows SYSTEM process? As I understand it, they are able to hurt the system e.g. by killing processes, uninstalling applications, replacing binaries, allocating memory, starting too many processes, .. Actually I could easily see a buggy remote system management update could just decide to uninstall everything and nuke the system, because it thinks it's stolen. And it would be designed functionality for it.