I don’t think that follows?
Stream still receives updates, and 0-day is literally unavoidable with any OS; 0-day means the vendor doesn’t know about it until it’s already in the wild, so no OS can be immune.
What does cause concern about Stream vs. a stable CentOS in the traditional sense is that software that works today may not work the next time you update. The long compatibility guarantee CentOS has historically given you, the strongest and longest in the free Linux distro world, is extremely valuable if you don’t want to have to babysit your servers every time you run an update.
A side effect of that “updates might break my servers” will be that people upgrade less often. Already many users are afraid to update the OS due to lack of understanding of how strong the compatibility guarantee in CentOS has been historically. Now, it’ll be more like Ubuntu (probably somewhere between LTS and the regular Ubuntu releases, but even LTS Ubuntu versions sometimes have breaking changes on minor version upgrades, so it may be more in line with that, we won’t know until we see how it’s implemented).
So, to be clear: I’m not gonna panic, and y’all shouldn’t either. I don’t like this change, as it means that when supporting CentOS we will always be in a state of “will it work today?” If it turns out to be much worse than Ubuntu LTS or Debian in that regard, it will be painful. We can manage it, if it’s on par with those…if it’s much worse than those, it will be hard. CentOS has always been my favorite server OS, despite its flaws (like very old versions even early in the release cycle), because I knew that if it worked today, it’d still work a year or three from now no matter how many software updates were applied. I’m much less confident of that for any other popular free distro (including Ubuntu LTS, which is probably second in line).
There are some benefits to a stream release cycle, too. CentOS may finally have reasonably new packages most of the time? But, reliability, stability, and predictability are gonna go down, by necessity. And, that will increase our load when supporting it and your load when using it on servers (but that may balance out by not having to jump through so many hoops to run recent versions of PHP or whatever).
Let’s just see how it plays out before we panic. As you know, switching distros with Virtualmin is mostly pretty easy. Not as easy as going from one CentOS version to the next, but not far from it. So, if we all have to migrate to Ubuntu LTS to maintain our sanity, we can. But, for now, Ubuntu LTS is quite a bit more problematic than CentOS on the dimensions we’re complaining about here…so I wouldn’t rush to switch, if you’re happy with CentOS today. That’s just signing on for the problems you foresee coming to CentOS a year before you need to.