> If a plumber/lawyer/<professional> offers services for free, and those services end up killing, or massively damaging someone, can they just say the same thing to absolve themselves of all liability?

There is a world of difference between what professionals such as doctors do and what free and open source developers do. It's not even remotely the same. I know because I happen to be both.

And even if they were in any way comparable, professionals get paid handsomely precisely because of the liability and responsibility. If people want this out of free software developers, they should start paying them some serious money.

> I also wish to change things, in the opposite direction.

If you want this, hire a professional to do it for you instead of pushing unwanted responsibility and liability onto the rest of us. I've got more than enough of that at my actual job and I absolutely do not want it in my free software development hobby. Adding liability to free software will kill it.

> FOSS devs should explicitly mark things as not-for-prod; rather than pushing things as prod-ready when they aren't.

It already is. Everything under a free or open source software license is already marked as such. The license says so. You use it at your own risk. Up to you to determine if that's good enough for you to use in production.