How in the heck???

My guess is that your facing whales and inactive players in bronze to gold rank. They're mostly challenge battles, so you don't have to worry about losing. You can simply surrender and look for another match. One thing to be wary about is tech users, they usually overwhelm you with powerful BUT expensive units. You can win if you charge the pad and harass their harvesters. Concentrate  your attack on one harvester and destroy any unit that tries to defend it.