Depends doesn't it.
I play for the challenge too. Some people play for the ability to experience a famous dynasty or period in history. Some people play for the ability to mod and tweak things (I do a lot of this). Some people play for a goal they set. There are lots of ways and reasons to play this kind of game.
Everyone can play the game as they please, of course. But the core of the game still revolves around making a long-lasting dynasty, which inevitably means competition against other players/characters.
Even if that was true (and it isn't, necessarily) it is ludicrous to say self-control isn't required in a 'competitive' game. These exploits aren't even part of standard gameplay, you have to go OUT OF YOUR WAY to make use of them. It is an active and concerted effort to skirt the game's intended playstyle. In a game that sprawls like CK2 does there will always be exploitable elements, holding the devs responsible for 'fixing' each and every one of those when the only thing a player has to do for it to not affect gameplay at all is TO NOT DO IT is ridiculous.
This one bug is far-fetched, I acknowledge that. But even then, the fact that there will always be exploitable elements does not exempt Paradox from having responsibility to fix any exploit they find.