> If a method is not generalizable to the entire dataset, it's not that useful.

No, in many situations, something doesn’t have to be perfect to be useful.

Again, I think you are missing the original point being made:

> Depending upon your use-case, you can get pretty good results by…

You seem to be responding as if I said:

> For all use-cases, you can get flawless results by…

Pointing out that this is not perfect is irrelevant to the point I was making. “Good enough” is usually good enough.