You can’t have it both ways. Either Ice Block is a tremendously powerful card, in which case disruption against it is good, or Ice Block isn’t that big a deal, and disruption against it is bad. Or more accurately, the better a card is, the more valuable its counter.
The truth is that Ice Block is good, but not as good as you’re making it out to be, so secret disruption is bad, but not quite as bad as you’re making it out to be.