That doesn't make sense. None of this has changed from previous updates and all previous macOS updates were far more stable than this one. This isn't a particularly feature laden update either.
But now all of a sudden we get catastrophic (deleted emails) and less catastrophic (missing Music playlists) data loss, crash bugs and generally weird behaviour of many apps.
I have identified one particular area where bugs are endemic: iCloud and it's complete failure to deal with multiple OS and client app versions. This is clearly a design issue as it also manifests itself in many ways that are not bugs as such.
For instance, Notes has gained the ability to share folders via iCloud. But if you create a folder and then share it from a device with the latest OS version, that folder disappears from all devices running older OS versions and importantly also from the icloud.com website.
Reminders on Catalina warns you of such version incompatibilities and the wording is telling. It's talking about "converting" something to the latest version. "Conversion" shouldn't even be a thing that users need to know about where no user controlled files are involved.
All indications are that there is a fundamental design error at the very core of iCloud's architecture. It feels like iCloud operates not as a single source of truth but as yet another device that participates in peer to peer syncing. This is a very complex architecture and they haven't been able to make it work.
So my conclusion is that iCloud which has always been exceptionally buggy has become pervasive within Apple's ecosystem. This is what has changed.