I've gotten a lot of knockouts back int the C- ranks because there were matches I was literally the only one employing any sort of strategy. Like it's not smart to stand next to the rain maker's shield when the other team blows it up! Crazy I know.
Obviously a lot of people are still very new to these modes so they won't know what to do, so it will take time before Ranked in this game resembles how it looked in Splatoon 1. You are likely seeing more knockouts because if one or two people are on a team who know what they are doing, then they will likely dominate and win the match very quickly. So far all my B- matches have been far more of a tug of war, though most have still been knockouts.
Even so, I feel like we had a better shot of making a comeback from what's I've played. I swear this game emphasizes getting people back into the fray quicker than Splatoon 1. I wipe the entire team out only to be battling them again within 15 seconds it feels. Or maybe it's because people overuse the jump feature, it's hard to say.