I will first start out by saying that yes, this game does have players that pay to play and have unlocked every card and maxed them out. HOWEVER, that doesnt mean that they are automatically going to win every game. Strategy and skill are VERY important in the game and thats how some people as a lvl 1 have beaten level 9s. (search videos on YouTube)
Having said that, I cannot give this game enough praise as after playing for a full year I have to say that it still makes me want to wake up and hop on to play before work or school. It not only passes the time, but is enjoyable while doing it. YES, you WILL HAVE LOSING STREAKS. Losing streaks can happen because of skill of the player, specific deck builds, or even internet connectivity issues. Please do not let these times deter you though because the game has developers that have (time and time again) proven to the community that it will constantly update the games and provide new ways to enjoy it. If you have recently given this game a try for a day or so and then got frustrated, you should reconsider. I have a gaming PC, Xbox One, and PS4 and yet I still find myself wanting to hop on this game when I am bored.
There have been things that have needed changed such as card damage/speed/count/health/glitches. However the developers do actually HEAR the community and there is even a support option if something were to go wrong with your individual account. After hearing the community, they make the changes necessarily to balance the game and that is what makes this game better than the rest. Not necessarily because its AD free, but because the developers listen and respond to the players.
Overall a game that I would and have recommended to anyone.