I don’t understand PVP

About month in f2p but I don’t understand PVP. I barely can win any fights unless they are like 300-500k less power than me (I’m 1.9M). I upgrade my team to get better but then I still have to fight people about the same power as me. My team comp is good, 2 earth defender and 3 not of this world. I don’t understand if everytime I level up I have to play people of my level when there is people higher up on the leaderboards in my rank with like 1 million less power.

I don’t get it tbh