Well in that case the simulator is full of it, because in my experience FG without support (or even often with support) is very likely to be a losing strategy. CR stats say it has a win rate with of 0.96 and win rate without of 1.06; this is better than Silver but nearly everything is better than Silver by that metric; my personal stats show a similar spread, and I buy it only 34 percent of the time.
Or how about looking at actual games? My game search page shows 14 instances where one person ended the game with at least 3 Fool's Golds and the other player had none: the Fool's Gold player had three wins, one tie, and
ten losses. That's not the mark of a broken card, not at all. It's the mark of a situational trap card. I think
this game is a particularly fun example, though
this one probably does a better job of refuting the idea that FG>Silver and Gold in treasure decks (yes, there was an engine, but it's the kind of engine that requires lots of actual treasure cards to work, and would have a better-than-average chance of lining up your FGs).
And, you know, even if it's the case that Fool's Gold is particularly good at BM or BM+X (I'll certainly agree that Fool's Gold is better than Silver in
Council Room games), the fact of the matter is that BM+X is rarely the best strategy, so that wouldn't bother me either.