The point is that decks that are good for advisor are bad against discard attacks. For example, over 9000 Pearl Divers? Great for Advisor. Bad against Militia. The presence of the discard attack makes you less inclined to pick up freebie cantrips, which makes your deck less suitable for Advisor, reducing the strength of the card.
I don't think this effect is ever going to be significant, but it does exist.
I still don't buy it. Cantrips are mostly bad against Militia in BM type situations because the lack of info about your next card really hurts (thus Pearl Diver sucking). I think that effect will be unnoticeable against an engine. And decks with Advisor don't really require a large number of cantrips, what they need badly is trashing ( and trashing is very good against discarding). But let's say the effect you're describing is real, do you think it outweighs the boost in strength that Advisor gets for mitigating the hand size reduction (and for engines being stronger in general with discarders)?
I'm not arguing about the strength of the effect at all, so I don't even want to go there. (I even said in my previous post that I think it's insignificant.) So let me lay out more explicitly the argument that
some effect exists, since you seem to be disagreeing with that.
As you mention, cantrips obscure information about your hand. This means cantrips are bad against Militia in all situations, including engines. For example, in a Village-Smithy engine, you want to have both a Village and Smithy in hand to get things started. If your draw is 5 Pearl Divers, you have no ability to ensure that when hit by Militia.
On the flip side, when one of the cards Advisor flips up is a cantrip, your opponent is denied information. That cantrip is effectively a random card from your deck. The best case is having Advisor flip up three identical cantrips, in which case it's a lab. That's even better than having Advisor flip up three great-but-different cards, because in that case your opponent can still discard the one that would help you most. Therefore cantrips are good with Advisor. (Whether Advisor
requires cantrips is irrelevant, and anyway I agree that Advisor doesn't require them.)
So we have two facts:
- Adding cantrips to a deck makes that deck worse against Militia.
- Adding cantrips to a deck makes that deck stronger with Advisor.
These are just two sides of the same coin: denying yourself information is bad, and denying your opponent information is good.
Here's why that indirectly makes buying Militia weaken your opponent's Advisors.
- If you don't buy Militia, your opponent is free to add cheap cantrips to your deck without penalty, which makes Advisor stronger because they are good with it.
- If you do buy Militia, your opponent might not want to add cheap cantrips to your deck, so without them, Advisor may be weaker in their deck than it otherwise would be.
Edit: Another example indirect anti-synergy would be Stables and Poor House. They don't directly interact much (and actually Stables's play effect may help Poor House by discarding treasure), but they like to live in different decks: Stables wants a deck that has decent treasure density, while Poor House wants all the treasure trashed.