I don't know about Adventurer at $2, it's comparable to a terminal Silver with the potential for quite a bit of upside so seems more in line with $3-4? I mean it doesn't really make much difference between 2, 3 and 4 in this case anyway.
I agree that the price doesn't matter much.
But let's nonethless play the price game: Adventurer is worse than
+2 Cards if you play an engine and better than
+2 Cards as you can skip green and purple. As Moat exists
+2 Cards would be weak at a price of $2 so the only question is whether the upsides or the downsides matter more.
I am pretty sure that most of the time the downsides overweigh: just like with Poor House you have to get rid of your Coppers and gain some villages and in addition to Poor House you need to add some Treasures to your deck to make Adventurer a decent payload card.
The last thing is the big issue; why would you want to waste terminal space if you need a few Silvers or Golds in your deck to enable this
conditional terminal payload card. It is not like
Gold vs Wine Merchant but
some Golds vs some Golds and Adventurer.
Also, if there is in addition to copper trashing and splitters terminal draw in the Kingdom this points more towards draw engine than Adventurer.
So Adventurer is competing with nearly every other type of card and mostly losing. The only thing that can save it IMO is something like what Asper did: +
1 Buy which might make it less than totally bad in Kingdoms without extra Buys.
On a sidenote, while Miser is often viewed as friendly Pirate Ship I think that one can also view it as an Adventurer fix: instead of 4 different cards you only need 2 now (no need for Copper trashers and Treasures).