I've never had any issues upgrading MacOS until Catalina. Every single step along the way has been buggy. From something as simple as trying to login to the Music app but it continually denies my correct username and password, to the iCloud connectivity issues Sidecar has attempting to connect to your ipad, and to the terrible Finder bug that doesn't refresh changes quick enough for you to access them. While there are solutions for most of these bugs, the process is tedious full of logging in and out of iCloud and restarting your various devices.
The entire experience has been awful. Catalina coupled with iOS 13 has objectively been one of the worst software releases by Apple, no matter how hard people who aren't experiencing problems try to paint it. A lot of the problems seem to be tied to iCloud. There's a reason there is article after article written about how buggy both are in comparison to last year.
At any rate, I think this post is going to attract mostly people who don't have problems just because your title is a little over the top and they'll want to come in and knock it down a peg. If you had simply expressed the problems you were having, it would probably be a more even discussion.