Don't let yourself get distracted...Mojave is far from being bug-free, but compared to Catalina...since 10.15.6 arrived it is just plain sure that Catalina will never ever reach the stability normally required for a productive environment. Maybe Big Sur will, maybe not...from my point of view it is not unlikely at all that macOS will remain as unstable as alternatives like Windows 10, maybe even worse considering the complexity of the current architecture shift and the insane amount of "features" announced at the WWDC ("features" in quotation marks as a feature which does not work reliably is IMHO worth much, much less than no feature at all)...bottom line, if you have a Mojave Installation which serves your needs, just stay with it, skip Catalina and hope Big Sur becomes a lot better than Bug-alina...the minor differences in Apps like Messages are certainly not worth the hassles...