Earlier quoted context omitted.
I've never quite gotten the problem with evergreening. The story is, a drug company seeing their patent expiration come up, makes some small improvement and patents that, getting them a new term. So far I'm following along. But the narrative is, this locks out generics somehow. The new patent can't cover the subject matter of the old patent, as its automatically prior art, so only the improvements are covered by the…
I think the missing step is likely the many millions dollars it takes to defend yourself in patent court. Even if you're likely to win, it brings a generic offering below profitability.
To a certain degree, it doesn't matter if your patent isn't completely valid, or doesn't completely match what your competitors are doing. The point is to have deeper pockets than them and be able to spend more on lawyers than them. As long as your patent lasts long enough in court to stop your competitors from doing whatever you don't want them to do, it has achieved its goal.
Patents are so broken.
(IANAL, just an MBA who's heard some war stories).