The lack of a feature is not the same as a bug.
A bug means that there is a feature, but it's not behaving as was specified. (Or expected, or as it used to ... but clearly a difference to something, not to nothing)
It doesn't matter whether to the end user that's indistinguishable. It is for us, the professionals.
It's the same as with any other profession and domain-knowledge. If my heater doesn't work but it used to work, that's a bug, a regression. If it doesn't integrate with my smart home, that's not a bug. It was never a feature to begin with.
> If you have a bug to fix to weigh against a feature to add, which do you pick? The only correct answer is "The one that provides most value".
I agree.
> And again we see that it's very possible - even likely - that fixing the last bug will _never_ be as important as adding more features.
Depends entirely on the project and the revenue stream. I've open sourced code which I consider done. It does what it should do and I won't any more features to it.
I will however fix bugs within the existing functionalities.