I think we’re long past the point where “hacking” in this sense has any sort of connotation of skill (and that is probably for the best). “Hack” is just a more colloquial synonym for “compromise”.

Nah, Nest could enforce 2FA, just as a basic example of how they could take responsibility for the safety of their consumers.

People seem to have adopted the term "hacking" to imply any and all unwanted access to a device or system. As far as I recall it meant that a device or system was modified in a way that was not originally intended. Logging in with the password is an intended use-case of the device, therefore not hacking in my opinion.

It's true, maintaining proper password hygiene is easy! See https://jasonlefkowitz.net/2015/09/ask-mr-science-how-to-sec... for details.

Legally, it is hacking.

I remember a story about someone getting an absurdly long prison sentence for guessing a simple password to a secure system.

Hacking only specifies the knowing and intentional circumvention of an authorization system. It doesn't place a value on how easy it was to do it.