Q: iTunes takes forever to do anything and can't even sync my phone

I'm running the latest version of iTunes on a Windows 10 PC trying to sync my iPhone 6. Whenever I open iTunes it takes a ludicrous amount of time to even open, I'm talking upwards of 10-15 minutes sometimes. Sometimes it even stops responding during this time and I have to try again. Sometimes it takes all that time to open and then it doesn't actually open (i.e. doesn't show up on the taskbar) so I have to double-click the icon again. Once I actually get it running and it finally registers that there's a phone plugged in and takes me to the page where I can sync it won't even sync. I click on the sync button but iTunes is so terrible it can't even do the sync without freezing (usually on 3/5 "coping diagnostic data") and then when it's done freezing and sorted itself out it just gets stuck on "waiting for changes to be applied" forever without actually doing anything. I have literally been trying to sync my phone since 6pm last night and it's 4:30pm as I write this.

Sorry for the rambling, I'm just really frustrated that I have to use such a dysfunctional program in 2015. Any help would be appreciated.