Japanese persuasion often works through suggestion rather than assertion, through hedging rather than declaration, through invitation rather than demand. This is not vagueness but respect. Indirect expression allows your audience to reach conclusions themselves, preserving their autonomy.
It manages face—if they disagree, they can simply not accept the suggestion rather than having to explicitly reject. It leaves room for adjustment. Direct, forceful assertion can seem arrogant and create resistance; it can threaten face if the listener must disagree openly. More tentative communication that leaves room for response may be more effective. Offer your views as considerations rather than conclusions, and let your audience arrive at agreement themselves.