I am no programmer, but one time someone explained to me that current software is much more buggier because its much more complex. He made a comparison saying, imagine an earthquake hits and skyscraper falls but a small hut stands still.
I personally hate the constant updates like it s a rolling release, I wish if we could go back when software was stable and updated it like once every 6 months. FireFox and Chrome has a new update almost on a weekly basis.
catalina here is as stable as any mac OS i've been on (actually, more stable than some earlier versions).