The thing is, in the beginning every player of this game started with low-level units. So there were plenty of other low-level opponents that you could get matched against. Now this is not the case anymore. All the people who have been playing for longer have decks that are considerably higher in level than yours, and there are not enough players with low-level armies online at any time of the day so that you could get such an opponent when needed.
Your choices are pretty much these:
1.) Keep playing, do the daily bounties every day, do the events, ask for cards and donate cards in a clan every day. You will make progress, but it will take months to level up.
2.) Spend an unreasonably high amount of money to level up your units fast.
3.) Stop playing.
