OP still isn't a coherent concept (OP -- over what?) but the ability to turn random +buys into spoils is pretty bonkers. Any cantrip +buy is going to have a field day with Alcove. Counterfeit will, too.
Card strength is not existing? Now that is a crazy notion.
There are obviously overpowered cards in Dominion, e.g. Cultist and Rebuild.
the "power" in "overpowered" (which is card strength) does exist. It's the "over" that makes no sense. Overpowered usually implies that a component makes one set of stuff stronger than another set of stuff. E.g., one unit makes a race stronger than another. Or one move makes one fighting character stronger than another. In dominion this doesn't apply since everyone has the same set of cards, so there's no equivalent to "character" or "race". And one
card being stronger than another, even far stronger, is a normal part of the game, both in terms of absolute strength and in terms of strength relative to the board. So if the only thing "over" (which is a comparative word) can target is other cards, and if it's not a bad thing if a card is stronger than other cards, well then "overpowered" is obviously not an applicable concept. (I've been saying this for years now.)
Case in point, Donate is much, much stronger than Cultist, but I don't see many people complaining about Donate. If strength itself were an issue, Donate would be a completely broken design. In fact, I would bet that if Donate were not an official card and someone posted it in a design threat, at least one person would call it overpowered and several people would agree with that person.
Donate of course has the property of not being spammable, but that just makes my point. If Cultist is a bad design, then it's because it dominates a strategy by itself, which donate does not. So it's not that about its card strength, it's about the effect of the card strength, so you need other properties as well to make the argument. Rebuild is an even better example, since it's not even all that strong (lots of 5$s are stronger), it just leads to very boring strategy when it is bought.