Nobody thinks that monument above seahag is... absurd?
I don't think it's absurd, but I do think it's wrong. Both are important cards because they can have a major effect on game pace. Sea Hag can do so by slowing down the game with junking, and Monument can extend it by offering an unlimited supply of points. The question is which of these effects is more valuable.
The problem with Sea Hag is that good trashing makes it pointless, since you give up a lot of tempo to get it by sacrificing a lot of early economy. The problem with Monument is that to actually get a lot of points out of it, you need a lot of spare terminal actions and a way of drawing all the villages and Monuments. Otherwise it's just a decently good terminal, giving you some score.
If you ignore Sea Hag without a good counter, you'll die, as your deck turns to junk. If you ignore Monument, you mgiht be okay a fair amount of the time, since if they can build something to reliably play Monuments, you can probably also build something to reliably buy Provinces.
I think overall Monument is useful less often, and less critical when it is useful, so all signs point to it being worse than Sea Hag overall. But I know WW absolutely loves Monument, so there's that... I guess when it's good, it's the centerpiece of your deck. Sea Hag is "just" an early-game thing (though I think early game is the most important part).