If you're being matched against more structured cards with 4x rares, I don't think you can. I'll assume this is standard.
Now I genuinely don't know if that's the case and I can't speak to the matchmaking. But some examples of cards you can get or run and general playstyle.
You'll want to press an early aggro and pressure their life. But still not play out your hand so you get 4 for 1d by a Kaya's wrath.
Run some non creatures who are good utility and still give you board presence after a kaya's wrath. Garruk 6, Garruk 4, Vivien 4, Vivien 5 are some examples. Great henge is a massive draw/ramp engine which also pumps your creatures.
Hand disruption is a favorite control hate form black. Duress, agonizing remorse.
Thrashing Brontodon gives a nice body which can also nuke enchantments.
heroic reinforcements lets your board survive a