> You can't have something better without changing it. It's a logical contradiction.

Sorry, that's a strawman. Of course you cannot have a better version without changing things. You definitely can have a better version without changing public API.

And people upgrade their toolchain not because they want a different API. They mostly want bugs fixed, support, and sometimes features. Breaking the API has a huge cost and minor benefit.

> It very much does because you don't need 95% of the random stuff in the crates.

But why does it matter if all that stuff comes in std or in an different crate? As I said security doesn't play a role here. You can't even avoid compile-time cost because the std can only come precompiled because it only changes with the toolchain, which is another downside we want to avoid.

> I guess that's one solution but it would probably just be a better idea to split std in two SLAs, one is guaranteed for core stuff i.e. the status quo, one is YMMV.

And again, how is that different from what I say, other than calling "official crates" as "std"?