I think that most people (especially on rank 20-15) can't afford to craft (or buy packs for it) new cards - especially legendaries and epics. That's why we still see decks that were popular in the previous expansion.
What a surprise that competitively minded people prefer to play proven, battle-hardened decks to climb the ladder. I mean, I'm not one of them and want to try out the new stuff but I can fully understand that a) some players don't have the resources to purchase packs or craft cards, b) hesitate to craft anything new until some kind of meta has been established due to them being afraid to waste dust or c) simply want to climb the ladder ASAP at any price. That shouldn't be an upset for you if you played competitive card games for a while to be honest.
You should rather expect to meet Bomb or Control Warrior, Mech or Midrange Hunter or Cyclone Mage and be glad if you queue into anything else. At least that's what I'm doing for now. For example, if I run into Control/Taunt Warrior and they tend to get the upper hand in the mid game I'll simply back off and let them have a wank since I'm clearly not willing to participate in a 30-45 min borefest. As long as T5 refuse to change Dr. Boom or nerf the deck so it has to run an actual win condition other than exhaustion I'd rather gift them their victory.