The key card is present but its support is thin.
Prioritize useful support such as Marauding Mako or Scrounging Skyray.
Deploy a discard payoff before Boosted Sloop, then declare one or more of your attackers. Sloop loots even if it stays home, producing one attack trigger and a discard event for your payoffs.
Your deck enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before another expensive payoff.
Boosted Sloop triggers for your attack, not an opponent's, and only once for that declaration. Cycling a payoff away does not leave it in play to reward later discards.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.