I'm also an iTunes user (running on Windows 7). It has a problem of its own like you said. I used to have a variety of problems with iTunes after upgrading it to newer versions. iTunes becomes extremely slow (it takes 5 minutes to get into the interface), can't detect my iPad Air or iTunes can detect the device but can't sync it and many other problems.
A few years ago, I stopped updating iTunes without uninstalling the current version first. I use the following article to uninstall iTunes in the correct order:
Remove and reinstall iTunes and related software components for Windows 7 and later - Apple Support
I just upgraded to the latest iTunes recently and it works flawlessly. It takes a couple of seconds to get to the interface and there is no problem with sync, backup etc. Read that article thoroughly and follow the direction step by step. Don't miss a step. You should be able to update it successfully.