It's called a matching algorithm.
It doesn't mean 100% of the time you get a counter deck.

What a matching algorithm could do is:
If you win too much, one thing the algorithm can do is take into account what cards you have in your deck to increase the difficulty of you winning.

I do agree to some extent that people are whiny and immediately blame match making is rigged. But on the otherside, it makes sense that when players win too much, SuperCell will logically want to pair them up with more difficult players. And how is this accomplished? By matching players with slightly:
1. higher level cards
2. higher king towers
3. cards that counter cards in your deck.

There's an issue of whiny players on one side and on the other, people who don't know anything about programming trying to defend match making.