Maybe "lazy" is too cruel of a word -- I was originally borrowing it from someone else's post -- but I just mean that printing narrow answer cards to solve problems is the easiest design task possible. It's much more difficult to design cards that, rather than directly shut down an existing oppressive strategy by reacting to it, proactively open up new angles of attack for other decks by enabling powerful new interactions that require tradeoffs to incorporate.
Lazy was my word, and I stand by it, for exactly the reason you've cited.
Here's a card I designed in 30 seconds. It would totally shake up Vintage. It would finally stick it to the evil Big Blue decks, and evil Dredge, and evil Shops. It would also increase format diversity: just stick 4 of these and some Moxen into your favorite Standard deck and you have something ready to take down Vintage champs.
Arbiter of Fairness
Players can't play more than one spell per turn.
Players can't take extra turns.
Nonbasic lands are Plains.
Players can't play cards from graveyards. Creatures can't enter the battlefield from any zone except the stack.
Is the Priest anywhere near this level? No, of course not. But I'm disappointed every time a new set contains a hatebear that is Vintage-playable only because it hoses the mechanics and interactions that make Vintage Vintage, rather than because it opens up novel proactive, powerful interactions on its own.