How can I replace a carrier-customized system with the original version? Is it possible to remove carrier customizations by just replacing whole system with the original version from phone manufacturer, just like we can reformat a computer and reinstall the operating system? Rooting, removing undesired apps, and other specific procedures that void warranty or do not ensure a clean stock install are a non-go.
It might be possible in some cases (I know Sony has released blobs before for ROM devs to use), but generally OEM's have agreements with carriers and release only carrier-laden ones. I know you said "without rooting", but you could technically flash a custom recovery and from there flash a "de-bloated" stock ROM from another developer. I know it's probably not really what you mean, but it does technically avoid rooting :P. That's probably going to be your best bet. Another, more ad-hoc option would be to freeze carrier apps (via titanium backup or something similar), and/or use alternative launchers like Nova or Apex to hide them from your app drawer. I don't think you need to be rooted to freeze an app, but I could be wrong. I feel your pain though, had an HTC Evo 4G back in the day. Never have I ever cared less about Sprint's sponsorship of NASCAR.