Those questions assume an existing framework where "the feature", "state of the art", "half-assed", and "failed" are all well-defined. But my experience is that the framing itself is most of where the challenge lies.

You end up with team A who wants to add the feature, team B who thinks it's an anti-feature, team C who thinks the entire application where feature lives should be scrapped, PM D who says users can already accomplish what the feature does using existing features, UX design E who says the fact that users are still asking for the feature means all those other features must be poorly designed and we should fix those...

That second paragraph summarized the last 5 years of my professional career.

In my experience, I've always listened to the last UX design E guy. Every time we worked on what he said the users asked for, we did well..

The problems caused by "half-assed" solutions are likely somewhere down the line, in distant future and their true costs impossible to estimate.

Anything less than perfection will incure avoidable future costs, and perfection approaches infinite time to deliver.

Ergo, standing in the present, one should do ones best to estimate future costs and decide what percent of perfection seems optimal.

In reality, when asked to self-estimate, too many teams (and especially naive PMs) select perfection as the optimal approach.