Well, in a vacuum, like, if you aren't counting your cards or tracking deck/discard at all, then Smithy has no effect on whether you have an action remaining when your action cards come around. The odds of drawing action cards dead is equally and oppositely opposed by the improved cycling, so over all it's a null, so your smithy is really just "+3$", (or maybe +2$ if you've got lots of those action cards running around).
WITH card counting, you might know that the remaining cards in your deck are dense with actions, so maybe you shouldn't play the Smithy. The most extreme case would be something like, the next three cards in your deck are certain to be Village, Smithy, Laboratory.
But, what happens in practice is that that kind of clump rarely happens. And if the thing you are considering is whether to draw Witch/Copper/Copper dead, then, yes the correct play is not to play the Smithy, but the real focus should be, why are you buying Smithy in a game where it is competing with such a powerful terminal?
It's a problem that will mostly come up in engine decks that somehow sputter when they shouldn't, and sometimes it is tricky to decide. You have to consider whether playing the Smithy will make you jump the 4-5$ gap anyhow, if it doesn't you should lean towards not playing it.