Some statements are true, some are just personal fears or related to your personal environment. I know about unaware CPU usage coming from so much different sources so that Windows itself have nothing to do about ( various trusted antiviruses, AMD Catalyst, so on and so forth)
rundll32 usage is also trigered by other software programs too.
Analyze your OS deeper and do not hurry up ranting it witout a very clear understanding of what is under the hood.
The Windows 10 update icon is something that bothered me too but by no mean that one add any extra usage on yor OS.
PS: Windows is curently a very mature OS and is very well optimized ( unix like approaches have been adopted too).