A late addition. I had an empty slot, and noticed that all of the large expansions gave you answers to the question, how do I deal with these dead victory cards? Intrigue has victory cards that aren't dead; Seaside lets you set them aside with Island, and, if you're crafty, Native Village; Prosperity has VP tokens; Hinterlands pushes card filtering. So I tried this out. Originally it didn't give +1 Action, but that version could not compete.
—Donald X. Vaccarino, The Secret History of the Dark Ages Cards
This is a very interesting quote. It suggests that Rebuild didn't reveal its true strength in either design or playtesting. Donald seems to have intended it as a VP-synergy card, rather than a game-winning action in its own right. And while a terminal Rebuild would certainly be a lot weaker, I don't think it would really be out of line with the other $5 actions in DA.
That makes a lot of sense to me. I didn't immediately recognize Rebuild's strength either, and I lost a lot of early games trying to "refute" my opponent's strategy of blindly spamming it. I expect that most of those opponents had themselves learned Rebuild's strength through similar experiences.
To me, Rebuild and Jack are the least "Dominion-like" cards in the game. They make for monolithic strategies where you ignore most of the board and do pretty much the same thing every turn. This is something that Dominion mostly avoids. I think the only other really monolithic cards are IGG, Governor, and maybe Minion and Cultist.
To me, the best thing about Dominion is the fact that it's always "broken," but it's broken in a different way every time. Broken games aren't fun once you figure out their tricks, but figuring out those tricks can be a lot of fun. Dominion lets you do that with every board... except when one of these monolithic strategy cards is around and you both already know the answer.
Don't get me wrong. I enjoy playing Governor and Minion games, and Rebuild mirrors gain a lot of sophistication from the fact that Duchies run out. But Jack, IGG, and Rebuild-vs-X races are mostly a baseball-like combination of tension and tedium. I don't mind playing these games from time to time, but I'm glad that most of my Dominion experiences are a lot more dynamic.