the thing about, lookout will completely cancel out one play of sea hag and you come out ahead because of the discard and +1 action. man, lookout's not even good
similarly, Counting House counters Ambassador, but we do not conclude that Ambassador is bad.
that's not what i said, necessarily. i said that the thing that happens when you play sea hag is completely negated by the thing that happens when you play lookout; in practice, ambassador beats the snot out of counting house, and it only gets worse when there's more cards of substance, and the strategy where you only get sea hags beats the snot out of only lookout, but remember that sea hag tries to take a card away from next turn and subsequent draws where you get the curse again, while costing a card and an action this turn, which, early on, means, sorry bud, what could've gotten a wharf this turn just gets its younger brother the fishing village. lookout, which is by all means a mediocre card, adds a card (on average, getting rid of an estate in favor of maybe drawing a copper or what have you) to next turn and future turns where you would have gotten that thing you trashed. in a good bit of cases they will completely cancel each other out.
there are legitimate empirical reasons, more elegant than my thing, that dictate that sea hag is a lot better than lookout (sea hag has a guaranteed ammunition of 10 curses, lookout might only work out 3 times with full efficiency and then less in the future, -1 vp, etc.) and, all being said, i contentedly have sea hag at #8 among 4s, perhaps higher, because there's a lot that it just doesn't let happen, but, man, sea hag doesn't help you at all, a lot of good cards do.