There have been lots of blogs about Apple's two new OS releases being "buggy", with Apple issuing corrective updates. Although I've upgraded to both OSes, I've been fortunate and haven't experienced any major issues. Why the "bugs", you might ask? The author of the following article was a software engineer at Apple for 18 years and offers his opinions on this question. Makes for an interesting read, should this be of interest to you.

Jim Hamm

https://tidbits.com/2019/10/21/six-reasons-why-ios-13-and-catalina-are-so-buggy/