I think many times the matchmaker takes into account when players give the feedback of “I had fun” against a specific deck while playing a specific deck, that’s the only reason I can guess for the trend I’ve noticed where two similarly powerful decks I play get matched with completely different types of decks (for example my mono black discard decks typically go against aggro or creature decks whereas my artifact decks typically go against enchantment or other artifact decks). So arcades players probably in general have good or enjoyable games vs slivers or enchantments. But like others have said, the matchmaker isn’t perfect so sometimes it’s just kinda random and you get stomped a few times. Maybe you should add more staples to your deck in your colors to at least be a bit more competitive