I've been talking about how it currently is. Not about how it could be in theory. And right now you will have a hard time finding any decks in the meta that have more than 3 hard removal spells. Sure they could play more, but they don't.
If you decide to not run big minions because of this that's your choice, but it's not a reasonable one. If you play 6 or more 5+ cards, and i have several decks that do that, then the chances are really really good that your opponent will run out of answers. Yes you won't draw all of them, just as your opponent won't draw all his removal, but if you have twice as many threats as he has answers, the chances are clearly in your favor. Yes, theoretically, if everyone starts doing that, they will probably stock up on hard removal, which in turn weakens them to other things causing the meta to shift into another direction.
The viability of big minion is certainly also a meta call, just like everything else in fact, but claiming they are useless or generally unviable is just plain wrong.